feat(app): a character card for kanji and kana

One card type for both (card schema 7): the character on the front, its
meanings and a kanji's on and kun readings, each merging on its own. A
kana's romaji is its meaning, so kana are studied, and later written,
exactly as kanji are. The composer offers it beside the other kinds, each
kind of reading on one line (ショク、ジキ); studying shows the character
large and, with the answer, its meanings and readings (the other way round
when asked from the back); the card browser filters by it and finds a kun
reading without its okurigana dot; the Markdown export writes its meanings
and readings.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01MMm7usAo6q9ZZRoPkWjoxi
Signed-off-by: Tizian 「ティツィアーン」 <raisondetredev@pm.me>

AGENTS.md

@@ -147,7 +147,7 @@ A spaced-repetition learning app: studysets of flashcards, reviewed on an FSRS s
   - **Dictionaries** (decided 2026-10-08): reference data the server holds for everyone, owned by no one, never synced (`dictionary_entry`, `dictionary_source`, `lib/src/dictionary/`). `halkyon_learn_curator` (AGPL, no Serverpod, so the server never links its code) turns each source's download into one format, a dictionary file (its README is the contract), with an adapter per source; a dictionary is one source in one meaning language (`jmdict` in `en`), of words or of characters (`kind`: JMdict, KANJIDIC2 with the kana), and the endpoints take it by those two, so a search for words never brings kanji; everything specific to a language (kana, romaji, meanings without "to") goes into each entry's `keys` and `looseKeys`, so the server's search knows no language: exact key, exact loose key, key starting with the query, loose key starting with it, each by the source's `rank` (`DictionaryEndpoint.search`, LIKE on barred keys, no extension needed). The server loads the files in its `dictionaries` folder at start, those whose SHA-256 changed, each source replaced in one transaction (`dictionary_loader.dart`). A card made from an entry copies what it needs and keeps `(source, sourceId)` as a soft reference only (`CardContent.entry`, card schema 6), so loading a newer version never touches cards. Every file carries its credits, which the app shows (About, and at the foot of the dictionary). In the app, a studyset's dictionary follows from its front language (`StudysetDictionary`, through `StudysetLanguageScope.of`): no attaching or detaching, and nothing dictionary-shaped shows without one (Add material › From the dictionary; Look up beside a vocabulary card's front). A word's example sentences (Tatoeba, through JMdict's examples edition) become its card's hints, up to three, the word in bold; Look up gives them to a card without hints of its own. `DictionaryAdder` makes the cards, each entry once per studyset, tagged `JLPT-NX` and with its word class by the first sense (`Noun`, `Verb`, `na-Adjective`); Look up in the composer gives a card the same tags (`DictionaryWord.tagNames`), and a word looked up again on that card swaps the tags the word before brought.
   - **The Pomodoro timer** (`feature/pomodoro/`): the profiles follow the person (`PersonSettings.pomodoro`, settings schema 4), the running timer is the device's own (`PomodoroRun` in `<person folder>/pomodoro.json`, `PomodoroRunStore`). `PomodoroRun` is a pure state machine on the time: a phase that ends leads to the next, running if its profile starts it by itself, else paused at its full length; a timer kept while the app was closed catches up (`caughtUpTo`). `PomodoroBloc` sits above the router (`PersonApp`), and `PomodoroPresenter` hands every change to `PomodoroPlatform` as a `PomodoroNotice` in the app's language, and its buttons back. **Android:** the app's own Kotlin (`PomodoroService.kt`; MethodChannel `app.halkyon.learn/pomodoro`, EventChannel `…/buttons`): a `specialUse` foreground service with a countdown notification (chronometer), Pause/Resume, Skip, Stop, on Android 16 a Live Update (`NotificationCompat.ProgressStyle`, the cycle's phases as segments, `setRequestPromotedOngoing`); an exact alarm (`USE_EXACT_ALARM`) alerts at the phase's end with the app closed; Do Not Disturb through the interruption filter, the one before kept in shared preferences and restored. With the app swiped away its buttons open it (a service may not start an activity from a notification's button since Android 12, so the notification is posted again with activity intents), and Stop works alone, leaving a mark the app takes at its next start (`takeStoppedOutside`) to forget its timer; a profile's next phase only starts by itself while the app runs. Dart's timers sleep with the device, so `PomodoroBloc` also looks every 15 s while a phase runs, and the alarm's receiver wakes it (`phaseEnds`); a kept timer is caught up before it first shows, or its ended phase would alert again. No notification plugin: flutter_local_notifications had Live Updates only in a prerelease needing compileSdk 37 (checked 2026-10-07). **Linux:** `LinuxPomodoroPlatform`, over package:dbus: where the top bar shows icons (GNOME with the AppIndicator extension, built into Ubuntu; KDE) the timer counts down there with its buttons in the icon's menu (`StatusNotifierItem`, written in Dart and laid out as libayatana-appindicator lays itself out, within the snap's rules, `desktop-legacy` of snapd v2.77: the item at `/org/ayatana/NotificationItem/<id>`, the only path the label's signal `XAyatanaNewLabel` may come from, registered with the watcher by that path, since a snap may bind no `org.freedesktop.StatusNotifierItem-*` name; the menu at `/MenuBar`; registered again when the watcher restarts); elsewhere the timer shows in the app alone, and on GNOME the Pomodoro card suggests the extension until dismissed, asking GNOME Shell to install or switch it on (`InstallRemoteExtension`, `EnableExtension`) or opening its page (decided 2026-10-07: no notification stands in; xdg-desktop-portal's Background status is for Flatpaks only). An alert with sound comes through `org.freedesktop.Notifications` when a phase ends while the app runs, and GNOME's `show-banners` goes off while focusing, through `gsettings`; the value before and the dismissed suggestion are kept in `<app support>/`. Calls to the bus go one at a time (`SerialQueue`).
   - **Citations** (`core/citation/`): a `Source` is plain text parts as the person typed them (authors as full names, one per line; year; title; `container`, what it is a part of; publisher; ISBN; link; `raw`, a citation a file brought, shown while nothing else is cited), and `formatCitation` cites it in the device's `CitationStyle` (APA 7, MLA 9, Chicago 18 notes and bibliography, decided 2026-10-07): it splits and abbreviates the names itself (inverted names, particles, suffixes; names written with `&` or "et al." stay as written), sets a work of its own in italics and a part of something apart from the whole by `container`, and writes a missing year as "n.d." in APA and Chicago. A step's sources (step schema 2) and a studyset's bibliography (`bibliography`, studyset schema 4, last writer wins like the rest of its payload) are lists of them, shown and changed through `SourceList` and `showSourcesSheet`, in reference-list order (alphabetical, whatever order they were added in); the path import reads them too, text as `raw` and the old format's `citation` as `container`.
-  - **What a card carries beside its type's fields** (card schema 5): up to six `hints` and an `explanation` (rich text, any type), a `report` that something on it is wrong (category, note, when; studied as before, its badge in the list), and a word's `senses` (glosses, label, JMdict's grammar codes, whose English short forms and meanings are data in `feature/card/model/jmdict_tags.dart`; with senses a word's meanings are their glosses, and `uk` on its first sense shows its reading from the start). Each merges as a field of its own. Deleting a card goes through `CardDeletions` (a `DelayedDeletions`, as notes and studysets), so the list and the session offer Undo. A study session's Undo takes back its steps last first (ratings, burials and deletions alike, across its rounds), so it holds the cards it deletes (`hold`) until it ends, when they go after the usual time to undo; a card deleted in a session that never ended (the app killed) stays. Vocabulary can be quizzed as multiple choice (`quizVocabulary`, `quizAspect` in the study options, settings schema 5; `vocabularyQuiz` draws the wrong answers from the other words studied).
+  - **What a card carries beside its type's fields** (card schema 5): up to six `hints` and an `explanation` (rich text, any type), a `report` that something on it is wrong (category, note, when; studied as before, its badge in the list), and a word's `senses` (glosses, label, JMdict's grammar codes, whose English short forms and meanings are data in `feature/card/model/jmdict_tags.dart`; with senses a word's meanings are their glosses, and `uk` on its first sense shows its reading from the start). Each merges as a field of its own. Deleting a card goes through `CardDeletions` (a `DelayedDeletions`, as notes and studysets), so the list and the session offer Undo. A study session's Undo takes back its steps last first (ratings, burials and deletions alike, across its rounds), so it holds the cards it deletes (`hold`) until it ends, when they go after the usual time to undo; a card deleted in a session that never ended (the app killed) stays. Vocabulary can be quizzed as multiple choice (`quizVocabulary`, `quizAspect` in the study options, settings schema 5; `vocabularyQuiz` draws the wrong answers from the other words studied). **A character card** (`CardType.character`, card schema 7, decided 2026-10-09: one type for kanji and kana) holds the character on its front, its `meanings` (a kana's romaji is its meaning, so kana are studied and written as kanji are) and a kanji's `onReadings` and `kunReadings` as dictionaries write them (katakana; hiragana with the okurigana after a dot); its JLPT level and school grade are tags, its strokes the app's own (KanjiVG).
   - **Imported cards** say where they came from in their first revision's payload (`origin`, card schema 3: `anki`, or `text` for flashcards pasted or read from CSV/TSV); the dashboard doesn't count them as written. The Anki import (`feature/anki/`) reads `.apkg`/`.colpkg` packages of every format on an isolate of its own (`AnkiPackageReader`), zstd through our fork of `pure_zstd` (Anki's frames don't record their size), and its fixtures come from Anki itself (`tool/anki/make_fixtures.py`).
   - **Every client migration keeps a device's rows** (`test/core/sync/device_migration_test.dart` replays each on a database with a row in every synced table of ours; SQLite rebuilds tables to add foreign keys, which Serverpod's runner does with foreign keys off). A new synced table needs a row in that test, which fails until it has one.
   - **Every synced table indexes `spaceId`** (`indexes: <table>_space_idx: fields: spaceId`, e.g. `studyset.spy.yaml`): deleting a space cascades into every synced table, and Postgres doesn't index foreign keys by itself, so account deletion and pruning would otherwise read whole tables.