feat(todo): dialogs on the desktop, the tabs reordered, a task's path and menu (ADR 0033, D11 to D14)

- halkyon_ui: showAdaptiveSheet shows a dialog on Linux, macOS and Windows
  at every width (bottom sheets stay on phones and tablets below expanded
  windows), so Learn and Train follow; SheetScaffold takes a heading in
  the title's place and may leave out its close button.
- Todo: the tabs are Inbox, Today, Upcoming, Browse, Today still opening;
  `serverpod start` launches the app on Linux, as it has no web build.
- A task's sheet shows where the task is (its project, an icon once tasks
  are above it, and the tasks above it, each opening what it names) and a
  ⋮ menu in place of its close button: when it was added (its UUID v7),
  Duplicate with its sub-tasks, hiding its done sub-tasks (synced in its
  payload), Close in the pane, Delete after asking. The description's icon
  stays by its first line.
- A row names its project and section at the end of its date's line; every
  menu entry has its icon.
- Learn: a studyset's path starts at the Library tab's icon, named by its
  tooltip.

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/todo/halkyon_todo_flutter/test/app/todo_app_test.dart

@@ -1,3 +1,4 @@
+import 'package:flutter/foundation.dart';
 import 'package:flutter_test/flutter_test.dart';
 import 'package:halkyon_app/halkyon_app.dart';
 import 'package:halkyon_app/testing.dart';
@@ -7,9 +8,11 @@ import 'package:halkyon_todo_flutter/src/core/privacy/todo_keys.dart';
 import 'package:halkyon_todo_flutter/src/feature/label/data/label_repository.dart';
 import 'package:halkyon_todo_flutter/src/feature/project/data/project_repository.dart';
 import 'package:halkyon_todo_flutter/src/feature/section/data/section_repository.dart';
+import 'package:halkyon_todo_flutter/src/feature/section/model/section.dart';
 import 'package:halkyon_todo_flutter/src/feature/task/data/task_repository.dart';
 import 'package:halkyon_todo_flutter/src/feature/task/model/repeat.dart';
 import 'package:halkyon_todo_flutter/src/feature/task/model/task.dart';
+import 'package:halkyon_todo_flutter/src/feature/task/widget/task_sheet.dart';
 import 'package:halkyon_todo_flutter/src/tabs/week_strip.dart';
 import 'package:halkyon_ui/halkyon_ui.dart';
 import 'package:lucide_icons_flutter/lucide_icons.dart';
@@ -166,6 +169,13 @@ void main() {
     await tester.pumpAndSettle();
   }
 
+  /// Closes the task's sheet as a tap beside it does: it has no close
+  /// button, its menu in the place of one.
+  Future<void> closeTaskSheet(WidgetTester tester) async {
+    await tester.tapAt(const Offset(20, 20));
+    await tester.pumpAndSettle();
+  }
+
   /// Opens Settings from Browse's cog (ADR 0033, D2).
   Future<void> openSettings(WidgetTester tester) async {
     await goTab(tester, 'Browse');
@@ -208,15 +218,15 @@ void main() {
   });
 
   group("Todo's frame (ADR 0033, D1 to D4)", () {
-    testWidgets('a phone has Today, Upcoming, Inbox and Browse, and opens on '
+    testWidgets('a phone has Inbox, Today, Upcoming and Browse, and opens on '
         'Today', (tester) async {
       await start(tester, usedBefore: true);
 
       expect(opened.single, FakeAuthGateway.person);
-      expect(tabs(tester), ['Today', 'Upcoming', 'Inbox', 'Browse']);
+      expect(tabs(tester), ['Inbox', 'Today', 'Upcoming', 'Browse']);
       expect(
         tester.widget<NavigationBar>(find.byType(NavigationBar)).selectedIndex,
-        0,
+        1,
       );
       expect(find.widgetWithText(AppBar, 'Today'), findsOneWidget);
     });
@@ -413,7 +423,7 @@ void main() {
       await tester.tap(find.text('Every day'));
       await tester.pumpAndSettle();
       expect(find.text('Every day'), findsOneWidget, reason: 'in the sheet');
-      await tester.tap(find.byTooltip('Close').last);
+      await closeTaskSheet(tester);
       await tester.pumpAndSettle();
       expect(
         find.descendant(
@@ -487,7 +497,7 @@ void main() {
       await tester.tap(find.text('Undated'));
       await tester.pumpAndSettle();
       expect(find.text('No reminders'), findsNothing, reason: 'no time');
-      await tester.tap(find.byTooltip('Close').last);
+      await closeTaskSheet(tester);
       await tester.pumpAndSettle();
 
       await tester.tap(find.text('Call the bank'));
@@ -515,6 +525,43 @@ void main() {
       );
     });
 
+    testWidgets("Today names a task's project and section on the line of "
+        'its date, at its end', (tester) async {
+      final today = Day.of(DateTime.now());
+      await start(tester, usedBefore: true);
+      final section = await tester.runAsync(
+        () => SectionRepository(
+          sectionRows,
+          keys,
+        ).add(SectionContent(name: 'Errands', projectId: inbox())),
+      );
+      sectionRows.bringRemoteChanges();
+      await seed(
+        tester,
+        TaskContent(
+          title: 'Feed the dogs',
+          projectId: inbox(),
+          sectionId: section,
+          date: TaskDate(today, time: 6 * 60),
+        ),
+      );
+
+      final where = find.text('Inbox / Errands');
+      expect(where, findsOneWidget);
+      final date = find.descendant(
+        of: find.widgetWithText(ListTile, 'Feed the dogs'),
+        matching: find.textContaining('06:00'),
+      );
+      expect(
+        tester.getCenter(where).dy,
+        moreOrLessEquals(tester.getCenter(date).dy, epsilon: 2),
+      );
+      expect(
+        tester.getTopRight(where).dx,
+        greaterThan(tester.getTopRight(date).dx),
+      );
+    });
+
     testWidgets('Today puts what is overdue first; Reschedule moves it to '
         'the day picked', (tester) async {
       final today = Day.of(DateTime.now());
@@ -612,7 +659,9 @@ void main() {
       await tester.pumpAndSettle();
       expect(find.text('Sub-tasks 0/1'), findsOneWidget);
 
-      await tester.tap(find.byTooltip('Delete task'));
+      await tester.tap(find.byTooltip('Task options'));
+      await tester.pumpAndSettle();
+      await tester.tap(find.text('Delete task'));
       await tester.pumpAndSettle();
       expect(
         find.text('"Pack" is deleted with its sub-task, on all your devices.'),
@@ -625,6 +674,128 @@ void main() {
       expect(await tester.runAsync(() => tasks().all()), isEmpty);
     });
 
+    testWidgets("a task's sheet shows where it is, the project as an icon "
+        'once tasks are above it, each step opening what it names', (
+      tester,
+    ) async {
+      await start(tester, usedBefore: true);
+      final list = await tester.runAsync(
+        () => tasks().add(TaskContent(title: 'Shopping', projectId: inbox())),
+      );
+      final dairy = await tester.runAsync(
+        () => tasks().add(
+          TaskContent(title: 'Dairy', projectId: inbox(), parentId: list),
+        ),
+      );
+      await seed(
+        tester,
+        TaskContent(title: 'Butter', projectId: inbox(), parentId: dairy),
+      );
+      await goTab(tester, 'Inbox');
+
+      await tester.tap(find.text('Shopping').first);
+      await tester.pumpAndSettle();
+      final path = find.byKey(taskPathKey);
+      expect(
+        find.descendant(of: path, matching: find.text('Inbox')),
+        findsOneWidget,
+        reason: 'a task of its own names its project',
+      );
+      await tester.tap(find.text('Dairy').last);
+      await tester.pumpAndSettle();
+      await tester.tap(find.text('Butter').last);
+      await tester.pumpAndSettle();
+
+      expect(
+        find.descendant(of: path.last, matching: find.text('Inbox')),
+        findsNothing,
+        reason: 'the project an icon once tasks are above',
+      );
+      expect(
+        find.descendant(
+          of: path.last,
+          matching: find.byIcon(LucideIcons.inbox),
+        ),
+        findsOneWidget,
+      );
+      expect(
+        find.descendant(of: path.last, matching: find.text('Shopping')),
+        findsOneWidget,
+      );
+      await tester.tap(
+        find.descendant(of: path.last, matching: find.text('Dairy')),
+      );
+      await tester.pumpAndSettle();
+      expect(
+        find.widgetWithText(TextField, 'Dairy'),
+        findsWidgets,
+        reason: 'the step opened in the sheet',
+      );
+    });
+
+    testWidgets("a task's menu says when it was added, duplicates it with its "
+        'sub-tasks and hides its done ones, on every device', (tester) async {
+      await start(tester, usedBefore: true);
+      final pack = await tester.runAsync(
+        () => tasks().add(TaskContent(title: 'Pack', projectId: inbox())),
+      );
+      await tester.runAsync(
+        () => tasks().add(
+          TaskContent(title: 'Socks', projectId: inbox(), parentId: pack),
+        ),
+      );
+      await seed(
+        tester,
+        TaskContent(
+          title: 'Passport',
+          projectId: inbox(),
+          parentId: pack,
+          completedAt: DateTime(2026, 10, 30),
+        ),
+      );
+      await goTab(tester, 'Inbox');
+      await tester.tap(find.text('Pack'));
+      await tester.pumpAndSettle();
+      expect(find.text('Passport'), findsOneWidget);
+      expect(find.byTooltip('Close'), findsNothing, reason: 'the menu instead');
+
+      await tester.tap(find.byTooltip('Task options'));
+      await tester.pumpAndSettle();
+      expect(find.textContaining('Added on '), findsOneWidget);
+      await tester.tap(find.text('Hide done sub-tasks'));
+      await tester.pumpAndSettle();
+      expect(find.text('Passport'), findsNothing);
+      final stored = await tester.runAsync(() => tasks().all());
+      expect(
+        stored!.firstWhere((t) => t.id == pack).content!.hideDoneSubTasks,
+        isTrue,
+      );
+
+      await tester.tap(find.byTooltip('Task options'));
+      await tester.pumpAndSettle();
+      await tester.tap(find.text('Duplicate'));
+      await tester.pumpAndSettle();
+      final after = await tester.runAsync(() => tasks().all());
+      expect(after!.where((t) => t.content?.title == 'Pack'), hasLength(2));
+      expect(after.where((t) => t.content?.title == 'Socks'), hasLength(2));
+    });
+
+    testWidgets('on the desktop a task opens in a dialog, however narrow '
+        'the window', (tester) async {
+      debugDefaultTargetPlatformOverride = TargetPlatform.linux;
+      addTearDown(() => debugDefaultTargetPlatformOverride = null);
+      await start(tester, usedBefore: true);
+      await seed(tester, TaskContent(title: 'Pack', projectId: inbox()));
+      await goTab(tester, 'Inbox');
+
+      await tester.tap(find.text('Pack'));
+      await tester.pumpAndSettle();
+
+      expect(find.byType(Dialog), findsOneWidget);
+      expect(find.byType(BottomSheet), findsNothing);
+      debugDefaultTargetPlatformOverride = null;
+    });
+
     testWidgets('Upcoming lists the days ahead, the empty ones too', (
       tester,
     ) async {
@@ -684,7 +855,7 @@ void main() {
       await tester.tap(find.text('Call Anna'));
       await tester.pumpAndSettle();
       expect(find.widgetWithText(TextField, 'Call Anna'), findsOneWidget);
-      await tester.tap(find.byTooltip('Close').last);
+      await closeTaskSheet(tester);
       await tester.pumpAndSettle();
 
       await tester.pageBack();
@@ -724,7 +895,9 @@ void main() {
         reason: 'what was typed is kept as another opens',
       );
 
-      await tester.tap(find.byTooltip('Close'));
+      await tester.tap(find.byTooltip('Task options'));
+      await tester.pumpAndSettle();
+      await tester.tap(find.text('Close'));
       await tester.pumpAndSettle();
       expect(find.byType(VerticalDivider), findsNothing);
 

apps/todo/halkyon_todo_flutter/test/feature/task/task_payload_test.dart

@@ -45,6 +45,7 @@ void main() {
     reminders: const [30, 0],
     completedAt: DateTime(2026, 11, 2, 7),
     completions: [DateTime(2026, 10, 19, 7, 5), DateTime(2026, 10, 22, 6)],
+    hideDoneSubTasks: true,
   );
 
   group('a task', () {
@@ -84,6 +85,7 @@ void main() {
           DateTime(2026, 10, 19, 7, 5).toUtc().toIso8601String(),
           DateTime(2026, 10, 22, 6).toUtc().toIso8601String(),
         ],
+        'hideDoneSubTasks': true,
       });
       expect(
         written(encodeTask(const TaskContent(title: 'Milk', projectId: 'p'))),

apps/todo/halkyon_todo_flutter/test/feature/task/task_repository_test.dart

@@ -177,6 +177,45 @@ void main() {
     },
   );
 
+  test('duplicating a task copies it with its sub-tasks, theirs too, right '
+      'after it among its siblings', () async {
+    final tasks = await device(alice);
+    final first = await tasks.add(milk.copyWith(position: 1));
+    await tasks.add(milk.copyWith(title: 'Next', position: 2));
+    final sub = await tasks.add(
+      const TaskContent(
+        title: 'Oat',
+        projectId: 'inbox',
+        position: 1,
+      ).copyWith(parentId: () => first),
+    );
+    await tasks.add(
+      TaskContent(
+        title: 'Bottles',
+        projectId: 'inbox',
+        parentId: sub,
+        completedAt: DateTime(2026, 11, 2),
+      ),
+    );
+
+    final copy = await tasks.duplicate(first);
+
+    final all = {for (final t in await tasks.all()) t.id: t.content!};
+    expect(all, hasLength(7));
+    expect(all[copy]!.title, 'Buy milk');
+    expect(all[copy]!.position, 1.5, reason: 'between it and the next');
+    final copiedSub = all.entries.singleWhere(
+      (e) => e.value.parentId == copy,
+    );
+    expect(copiedSub.value.title, 'Oat');
+    expect(copiedSub.key, isNot(sub));
+    final copiedBottles = all.values.singleWhere(
+      (t) => t.parentId == copiedSub.key,
+    );
+    expect(copiedBottles.title, 'Bottles');
+    expect(copiedBottles.completed, isTrue, reason: 'copied as it was');
+  });
+
   test("deleting a project's or a section's tasks deletes only theirs, "
       'with their sub-tasks', () async {
     final phone = await device(alice);

apps/todo/halkyon_todo_flutter/test/feature/task/task_views_test.dart

@@ -106,4 +106,14 @@ void main() {
       ],
     );
   });
+
+  test('a task was added when its UUID v7 says, its first 48 bits the '
+      'milliseconds since 1970; another ID says nothing', () {
+    expect(
+      addedAt('019a3e2f-8c00-7000-8000-000000000000'),
+      DateTime.fromMillisecondsSinceEpoch(0x019a3e2f8c00),
+    );
+    expect(addedAt('not-an-id'), isNull);
+    expect(addedAt('019a3e2f-8c00-4000-8000-000000000000'), isNull);
+  });
 }