feat(learn,todo,train,meditate,ui): the navigation bar flush with the foot, a fade above it

Below medium windows the frame's bar is Material 3 Expressive's again,
flush with the window's foot (decided 7 Nov 2026 by the developer): the
theme's NavigationBar across the whole width, 64 dp in its own colour,
running on beneath the system's bar as Material's does. Right above it a
fade 32 dp high, from the background of the screen in view (the
ScreenTint's, the theme's surface before a screen claims one) made
see-through to that background, so what scrolls on beneath the bar fades
out rather than being cut off; taps pass through it. The rail of wider
windows stays as it was.

halkyon_ui's FloatingNavigationBar becomes FlushNavigationBar, its side
margin, lift and rounded card gone. Its coverOf is now the whole room
content leaves at its end, the system's bar included (the body's bottom
padding: bar, fade and system's bar inside the frame, the system's bar
alone outside it), and floating buttons rise by buttonLiftOf, the same
without the system's bar, which a Scaffold keeps them clear of itself.
Lists, Todo's hour grid and the Plan's sheet keep using coverOf; the
Profile's list no longer adds the system's bar a second time.

Whats-New: The navigation bar sits at the bottom edge again, with a soft fade above it.
Whats-New-De: Die Navigationsleiste sitzt wieder am unteren Rand, mit einem sanften Übergang darüber.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Signed-off-by: Tizian 「ティツィアーン」 <raisondetredev@pm.me>

apps/learn/AGENTS.md

@@ -35,9 +35,9 @@ A spaced-repetition learning app: studysets of flashcards, reviewed on an FSRS s
 - **UTC for storing and sending, local time for display and day boundaries.** Serverpod sends `DateTime` as UTC and stores it in `timestamp without time zone` columns. Compare and compute in UTC; call `.toLocal()` only to display. "Due today", streaks and daily goals use the learner's **local** calendar day, computed on the client; the server never needs day boundaries.
 - **Build configuration comes from `--dart-define`.** The client holds no secrets, ever.
 - **Material comes from `package:material_ui`** (Cupertino from `package:cupertino_ui`), never from `package:flutter/material.dart`, which Flutter deprecates from its November 2026 release on. Packages still on the SDK's copy get the app's theme and localizations through `MaterialUiCompatibilityBridge` in `MaterialApp.builder`; remove it once they have moved.
-- **Navigation is `go_router`**: the routes in `lib/src/app/app_router.dart`, their paths in `core/router/route_paths.dart`. Four tabs (Home, Library, Explore, Profile) are the branches of a `StatefulShellRoute`, each keeping its own stack of screens alive while another tab shows (`tabsContainer`, halkyon_ui's `TabsStack`: go_router's indexed stack plus `TabVisibility`, which a screen depends on to stop something once its tab is hidden); `AppShell` shows them through halkyon_ui's `NavigationFrame`, every Halkyon app's (decided 2026-10-30), as a navigation rail from 600 dp on and as a navigation bar below (Material 3 Expressive's shorter one, 64 dp, set in the theme: Flutter's Material library has none yet), floating above the bottom edge (`FloatingNavigationBar`): the tab screens run on beneath it (the shell's `extendBody`), every list ending with room for it (the body's bottom padding) and floating buttons lifted by `FloatingNavigationBar.coverOf`, with the background of the screen in view around it in between (`ScreenTint`); it steps aside inside a studyset (its screen, notes, paths and dictionary: `RoutePaths.isInsideStudyset`), whose own bar at the bottom takes its place, leaving a strip as high as the system's bar (decided 2026-10-11, as Material 3 puts toolbars below the top level and Vaia does), and choosing the open tab again returns to its first screen. A tab's own screens are routes nested in its branch, reached with `context.go` (a studyset's screen in the library), and **the screens behind a studyset are its path** (decided 2026-10-11; `feature/studyset/widget/studyset_navigation.dart`): a topic, at any depth, opens with the screens of the levels between pushed beneath it (`openStudysetWithin`; the same route, keyed by id and named by its location, so several stack), the path's steps and the levels a long press on back lists go up by popping to that page (`goUpTo`), and a studyset opened from elsewhere gets its levels beneath it (`openStudyset`). So back, Android's predictive back, iOS's swipe from the edge and the path all lead one level up. Below expanded windows the topics open in a sheet from the end of the path's line, never a drawer, whose swipe from the edge is iOS's way back. A studyset's notes and learning paths (working through one, writing it, writing a step) are routes of the Library branch too, so the tabs stay beside them. What needs the whole window (studying, a card, a PDF, settings) is a top-level route over the tabs, reached with `context.push`. Explore lists what is published (see *Explore and copies*).
+- **Navigation is `go_router`**: the routes in `lib/src/app/app_router.dart`, their paths in `core/router/route_paths.dart`. Four tabs (Home, Library, Explore, Profile) are the branches of a `StatefulShellRoute`, each keeping its own stack of screens alive while another tab shows (`tabsContainer`, halkyon_ui's `TabsStack`: go_router's indexed stack plus `TabVisibility`, which a screen depends on to stop something once its tab is hidden); `AppShell` shows them through halkyon_ui's `NavigationFrame`, every Halkyon app's (decided 2026-10-30), as a navigation rail from 600 dp on and as a navigation bar below (Material 3 Expressive's shorter one, 64 dp, set in the theme: Flutter's Material library has none yet), flush with the bottom edge (`FlushNavigationBar`, decided 7 Nov 2026 by the developer in place of a bar floating above it: Material 3 Expressive keeps the bar flush, 64 dp, and a fade replaces the floating card), with a fade 32 dp high above it into the background of the screen in view (`ScreenTint`), which taps pass through: the tab screens run on beneath both (the shell's `extendBody`), every list ending with room for them (the body's bottom padding, `FlushNavigationBar.coverOf`: the bar, its fade and the system's bar) and floating buttons lifted by `FlushNavigationBar.buttonLiftOf` (the same without the system's bar, which a Scaffold keeps its button clear of itself); it steps aside inside a studyset (its screen, notes, paths and dictionary: `RoutePaths.isInsideStudyset`), whose own bar at the bottom takes its place, leaving a strip as high as the system's bar (decided 2026-10-11, as Material 3 puts toolbars below the top level and Vaia does), and choosing the open tab again returns to its first screen. A tab's own screens are routes nested in its branch, reached with `context.go` (a studyset's screen in the library), and **the screens behind a studyset are its path** (decided 2026-10-11; `feature/studyset/widget/studyset_navigation.dart`): a topic, at any depth, opens with the screens of the levels between pushed beneath it (`openStudysetWithin`; the same route, keyed by id and named by its location, so several stack), the path's steps and the levels a long press on back lists go up by popping to that page (`goUpTo`), and a studyset opened from elsewhere gets its levels beneath it (`openStudyset`). So back, Android's predictive back, iOS's swipe from the edge and the path all lead one level up. Below expanded windows the topics open in a sheet from the end of the path's line, never a drawer, whose swipe from the edge is iOS's way back. A studyset's notes and learning paths (working through one, writing it, writing a step) are routes of the Library branch too, so the tabs stay beside them. What needs the whole window (studying, a card, a PDF, settings) is a top-level route over the tabs, reached with `context.push`. Explore lists what is published (see *Explore and copies*).
   - **Routes carry ids, never objects.** A screen finds its item in the repository's live list with `FoundById`: a spinner until the list arrives, then the item, or a screen saying it no longer exists (deleted on another device, or an old link). A screen that deletes its item closes, and keeps showing the item while it goes. Why: every location can be built from its path alone, and no screen goes on showing something that has gone.
-- **The look is one theme, every Halkyon app's**: the theme, its fonts, the window sizes and the shared widgets come from `halkyon_ui` (`packages/halkyon_ui`, decided 2026-10-18). Change them there, not here. `appTheme(brightness, extensions:)` with hand-written light and dark colour schemes around the brand's cobalt and copper, which Learn calls as `learnTheme` (`core/theme/`) with its own colours beside; `Theme.of(context).extras` (`ThemeExtras`) for the states Material has no role for, and `Theme.of(context).learnColors` (`LearnColors`) for Learn's own (the four FSRS ratings, a starred star); `PaletteColor` for the 20 colours a person can give content; snack bars floating above the navigation bar as Material 3 places them, in its inverse colours (dark in the light theme), lined up with the floating bar, 560 wide and centred from medium windows on (`FittedSnackBars`, decided 2026-10-12; Flutter's default is Material 2's fixed bar across the foot); `TopGradient` for a colour washing down from the top of every tab's first screen and Settings (cobalt) and of every screen of a studyset (its colour, own or inherited, which `_inStudyset` in the router hands down as `ScreenColor`): the studyset, studying it, its cards, writing them, its notes, paths and dictionary; behind a clear app bar, in dark mode a deep shade (42 % of the colour over black), in light mode a tint, held to WCAG AA for the theme's text. From medium windows on, a `TintFrame` takes the colour of the screen in view (`ScreenTint`, claimed by the `TopGradient` whose tab shows and whose route is on top), fading out by 60 % of the height: the rail sits on it, transparent, and the screen is a rounded panel inset beside it, its own wash half as strong; screens over the tabs (studying, the card browser and composer, Settings) sit in the same frame without the rail (`FramedScreen`). As Vaia does, decided 2026-10-10. The PDF reader and the reading timeline stay plain. halkyon_ui's `theme_test.dart` holds text to WCAG AA contrast (4.5:1) on each palette colour and on the dark theme's primary colour and surface, and Learn's `learn_theme_test.dart` a starred star to 3:1 on the cards. **Fonts are bundled, never fetched** (halkyon_ui's `app_fonts.dart`; the CJK fonts are the app's own, `assets/fonts/ATTRIBUTION.md`, their licence registered by `core/theme/cjk_fonts.dart`, under the families halkyon_ui's fallback names): Noto Sans, from halkyon_ui, is the app's font on every device (Latin, Greek with polytonic, Cyrillic); Noto Sans JP, SC, TC and KR fill in Japanese, Chinese and Korean, Japanese first unless a studyset's language puts its own first (`StudysetLanguageScope`, which every studyset route wraps its screen in through `_inStudyset`, and the library's and Explore's cards each around their studyset; Han characters take the first listed font's shapes); each is one variable font holding every weight, and their OFL licences join the licence list. Scripts none covers (Arabic, Hebrew, Thai, …) fall back to the device's own fonts. A studyset's languages (`frontLanguage`, `backLanguage`, BCP 47) are given together or inherited together from the nearest studyset above (`languagesOf`). Never add `google_fonts` or anything else that downloads fonts. Layouts follow Material 3's window-size classes (`context.windowSize`), and running text stays within `readableContentMaxWidth`. Icons are Lucide (`lucide_icons_flutter`), except a starred star and the marks of a choice not yet checked (filled box and circle), which need the fill Lucide lacks; the Material icons left in older screens go when those are restyled. Shared widgets come from halkyon_ui (`SectionCard`, `AppLoadingIndicator` (every spinner is Material 3 Expressive's, in buttons `ButtonLoadingIndicator`, pulling a list down `AppRefreshIndicator`, never Flutter's older circular one), `confirmDestructiveAction`, `FoundById`, `TitleWithKicker`, `showUndoSnackBar`, `ScrollHidingFab`, `PaletteColorPicker`, `CountStepper`, `requiredDecoration` (every required field: while empty its outline stronger, in the primary colour, and "Required" below it; never an asterisk) and `FieldInfoButton`, `ReorderToggle`, `ReorderGrip`, `CollapsingRow`, `CountBadge`, `liftWhileDragged`, `LaunchScreen` and `BrandWordmark` ("Halkyon" over an app's word), `SliverCentered` and `EmptyListMessage` (what an empty list shows: icon, "No … yet", and which menus add some), `Shimmer` and `SkeletonBox` (what a list shows while it loads in place of a spinner, the Library's cards since 1 Nov 2026), and the sheets below), with texts of their own (`HalkyonUiLocalizations`); Learn's own are in `core/widget/` (`ConflictVersions`, the versions of a conflict each editor shows, with Keep, its save status beside it `SaveStatusLabel` in `core/editor/`; `ContentCountsLine`; `AppLaunchScreen`, what shows while the app opens: the kingfisher, "Halkyon" over "Learn", whose wordmark the first start shows too).
+- **The look is one theme, every Halkyon app's**: the theme, its fonts, the window sizes and the shared widgets come from `halkyon_ui` (`packages/halkyon_ui`, decided 2026-10-18). Change them there, not here. `appTheme(brightness, extensions:)` with hand-written light and dark colour schemes around the brand's cobalt and copper, which Learn calls as `learnTheme` (`core/theme/`) with its own colours beside; `Theme.of(context).extras` (`ThemeExtras`) for the states Material has no role for, and `Theme.of(context).learnColors` (`LearnColors`) for Learn's own (the four FSRS ratings, a starred star); `PaletteColor` for the 20 colours a person can give content; snack bars floating above the navigation bar as Material 3 places them, in its inverse colours (dark in the light theme), 16 in from the sides and 8 above the bar's fade, 560 wide and centred from medium windows on (`FittedSnackBars`, decided 2026-10-12; Flutter's default is Material 2's fixed bar across the foot); `TopGradient` for a colour washing down from the top of every tab's first screen and Settings (cobalt) and of every screen of a studyset (its colour, own or inherited, which `_inStudyset` in the router hands down as `ScreenColor`): the studyset, studying it, its cards, writing them, its notes, paths and dictionary; behind a clear app bar, in dark mode a deep shade (42 % of the colour over black), in light mode a tint, held to WCAG AA for the theme's text. From medium windows on, a `TintFrame` takes the colour of the screen in view (`ScreenTint`, claimed by the `TopGradient` whose tab shows and whose route is on top), fading out by 60 % of the height: the rail sits on it, transparent, and the screen is a rounded panel inset beside it, its own wash half as strong; screens over the tabs (studying, the card browser and composer, Settings) sit in the same frame without the rail (`FramedScreen`). As Vaia does, decided 2026-10-10. The PDF reader and the reading timeline stay plain. halkyon_ui's `theme_test.dart` holds text to WCAG AA contrast (4.5:1) on each palette colour and on the dark theme's primary colour and surface, and Learn's `learn_theme_test.dart` a starred star to 3:1 on the cards. **Fonts are bundled, never fetched** (halkyon_ui's `app_fonts.dart`; the CJK fonts are the app's own, `assets/fonts/ATTRIBUTION.md`, their licence registered by `core/theme/cjk_fonts.dart`, under the families halkyon_ui's fallback names): Noto Sans, from halkyon_ui, is the app's font on every device (Latin, Greek with polytonic, Cyrillic); Noto Sans JP, SC, TC and KR fill in Japanese, Chinese and Korean, Japanese first unless a studyset's language puts its own first (`StudysetLanguageScope`, which every studyset route wraps its screen in through `_inStudyset`, and the library's and Explore's cards each around their studyset; Han characters take the first listed font's shapes); each is one variable font holding every weight, and their OFL licences join the licence list. Scripts none covers (Arabic, Hebrew, Thai, …) fall back to the device's own fonts. A studyset's languages (`frontLanguage`, `backLanguage`, BCP 47) are given together or inherited together from the nearest studyset above (`languagesOf`). Never add `google_fonts` or anything else that downloads fonts. Layouts follow Material 3's window-size classes (`context.windowSize`), and running text stays within `readableContentMaxWidth`. Icons are Lucide (`lucide_icons_flutter`), except a starred star and the marks of a choice not yet checked (filled box and circle), which need the fill Lucide lacks; the Material icons left in older screens go when those are restyled. Shared widgets come from halkyon_ui (`SectionCard`, `AppLoadingIndicator` (every spinner is Material 3 Expressive's, in buttons `ButtonLoadingIndicator`, pulling a list down `AppRefreshIndicator`, never Flutter's older circular one), `confirmDestructiveAction`, `FoundById`, `TitleWithKicker`, `showUndoSnackBar`, `ScrollHidingFab`, `PaletteColorPicker`, `CountStepper`, `requiredDecoration` (every required field: while empty its outline stronger, in the primary colour, and "Required" below it; never an asterisk) and `FieldInfoButton`, `ReorderToggle`, `ReorderGrip`, `CollapsingRow`, `CountBadge`, `liftWhileDragged`, `LaunchScreen` and `BrandWordmark` ("Halkyon" over an app's word), `SliverCentered` and `EmptyListMessage` (what an empty list shows: icon, "No … yet", and which menus add some), `Shimmer` and `SkeletonBox` (what a list shows while it loads in place of a spinner, the Library's cards since 1 Nov 2026), and the sheets below), with texts of their own (`HalkyonUiLocalizations`); Learn's own are in `core/widget/` (`ConflictVersions`, the versions of a conflict each editor shows, with Keep, its save status beside it `SaveStatusLabel` in `core/editor/`; `ContentCountsLine`; `AppLaunchScreen`, what shows while the app opens: the kingfisher, "Halkyon" over "Learn", whose wordmark the first start shows too).
 - **A studyset's options are the same wherever a menu of it opens** (`studysetOptions` and `doStudysetOption` in `studyset_actions.dart`, decided 2026-10-12): its card in the library, its own screen, a topic beside it. Import content runs where the studyset's blocs are, on its screen: from elsewhere it opens the screen, which asks what to import as it opens (`?import=content`).
 - **A studyset's content is in three parts** (`feature/studyset/widget/studyset_parts.dart`, decided 2026-10-12, as Vaia has it): Material (its learning paths, flashcards, notes and files in tabs, the paths first as the way through the rest (decided 2026-10-13: a path is material too, which the plan refers to), each saying how many it holds, an empty one nothing so the four fit a phone more often, each list whole with its tools at the end of the tabs' row, which fold one by one where room runs short rather than cutting the tabs off (`CollapsingRow`: Browse's words first, then the filter into the ⋮ menu, then Browse; as the studyset's own actions fold into icons); decided 2026-10-12 after a trial of sections one below the other, the first three of each behind Show all, as Vaia stacks them: the lists run to hundreds of cards, and tabs are Material 3's way within a part; the tab is kept as the studyset's part, while the material shows, and opened for the first time it opens on the first tab with something in it; a tab with none of its own while the studyset's topics hold some says that it is in them, each topic holding some with how much, everything inside it counted, opening it, Browse all for flashcards, and how to add some here after all, decided 2026-10-14 after people testing the app looked for a grouping studyset's material in its empty tabs; the tabs' counts stay its own), Progress (always, nothing yet where nothing was studied, so the switch never changes as reviews are read, decided 2026-10-12: how much is learnt, what is due today, the study time this week from the reviews' durations, each at most `Review.maxStudyTime`, `StudysetActivityCubit`; how many steps of its learning paths are done and the PDFs not read to their end, begun first, each opening the reader, decided 2026-10-17: `MaterialProgressCubit`; all of it across its topics) and Study plan (the paths finished; Next up: studying for the exam while one is ahead and its pace leaves cards for the day, then the cards due, then the next step of each path under way, or the first path not finished when none is; how far each path has come, its steps done in a bar, each opening the path; managing the paths is the material's; at the top the exam the person prepares for, below; `PathListState.stepsDone`). `StudysetPartSwitch` chooses between them in the header: below expanded windows in a line of its own under the title, from there on in the path's line, which the topics leave free there, centred above the material's column (at the line's end where that column is narrower than the switch; the path folds before it); it ticks as the navigation bar does. **A studyset opens on the part it was left on, on this device** (`StudysetTabs`, `studyset_tabs.json` in the person's folder, read as their data opens, decided 2026-10-11; a tab kept before the parts counts as its part); opened there for the first time, on the study plan while a path is unfinished, else on the material, showing that it loads until it knows rather than one part and then another. Material added or imported shows in its part (`ContentTabCubit`).
 - **Statistics** (`feature/statistics/`, decided 2026-10-12, as Vaia has them): the Profile tab's second tab (the tab row folding into the title as the content scrolls, halkyon_ui's `FoldingTabs`, as Strava's). The time studied in all, per day (every day from the first studied to today counted) and the most in one day, and by days, weeks or months (ten, ten, twelve bars) the study time and the ratings, as bars the app draws itself (`BarChart`, no chart package); a tap on a bar says what it holds. Computed on the device from every review (`studyStatistics`, `StatisticsCubit`), every rating counted, crammed ones too, a fresh start not, and **a review counts as at most a minute of study** (`Review.maxStudyTime`, as Anki does by default: a card left on the screen over lunch isn't an hour of study; stored durations stay as they were), here and in a studyset's Progress. What waits in Recently deleted counts nowhere, here or on Home.