feat(learn): a Viewer suggests new flashcards and notes

ADR 0044's step 6b (D48) in the app: where an Editor has Add material, a
Viewer of a shared studyset has Suggest material, offering a flashcard
or a note. The composer and the note editor open suggesting from the
start, saying that what is suggested joins the studyset once its owner
or an editor takes it in; Send suggestion asks why, and Cancel or
sending closes it. Nothing is written into the studyset: the fields go
into the suggestion alone, which goes into the Viewer's own space as
the changes they suggest do.

Whats-New: In a studyset shared with you as a viewer, Suggest material proposes a new flashcard or note to its owner and editors.
Whats-New-De: In einem Lernset, das du nur ansehen darfst, schlägst du über „Material vorschlagen“ neue Karteikarten und Notizen vor.

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/halkyon_learn_flutter/test/feature/sharing/view_only_test.dart

@@ -238,6 +238,105 @@ void main() {
     );
   });
 
+  testWidgets("a Viewer's studyset offers to suggest a flashcard or a note, "
+      'never to add one', (tester) async {
+    shared(viewOnly: true);
+    await showApp(tester, RoutePaths.studyset('japanese'));
+
+    expect(find.text('Add material'), findsNothing);
+    await tester.tap(find.text('Suggest material'));
+    await tester.pumpAndSettle();
+
+    expect(find.text('Suggest a flashcard'), findsOneWidget);
+    expect(find.text('Suggest a note'), findsOneWidget);
+    expect(find.text('Create flashcards'), findsNothing);
+    expect(find.text('Create a note'), findsNothing);
+  });
+
+  testWidgets('an Editor adds material, suggesting none', (tester) async {
+    shared(viewOnly: false);
+    await showApp(tester, RoutePaths.studyset('japanese'));
+
+    expect(find.text('Add material'), findsOneWidget);
+    expect(find.text('Suggest material'), findsNothing);
+  });
+
+  /// Opens what a Viewer suggests anew from the studyset's menu: [item],
+  /// "Suggest a flashcard" or "Suggest a note".
+  Future<void> suggestNew(WidgetTester tester, String item) async {
+    shared(viewOnly: true);
+    await showApp(tester, RoutePaths.studyset('japanese'));
+    await tester.tap(find.text('Suggest material'));
+    await tester.pumpAndSettle();
+    await tester.tap(find.text(item));
+    await tester.pump();
+    await tester.pump(const Duration(seconds: 1));
+    await tester.pumpAndSettle();
+  }
+
+  testWidgets("a Viewer's new note goes as a suggestion for the studyset, "
+      'which it joins only once taken in', (tester) async {
+    await suggestNew(tester, 'Suggest a note');
+
+    // Suggesting from the start, with nothing to change.
+    expect(
+      find.textContaining('suggesting something new', findRichText: true),
+      findsOneWidget,
+    );
+    expect(find.text('Suggest a change'), findsNothing);
+    await tester.enterText(find.byType(TextField).first, 'Particles が');
+    await tester.pump();
+    await send(tester, 'The other particle.');
+
+    final thread = written.threads.single;
+    expect(thread.space, 'space-1');
+    expect(thread.json['target'], {
+      'kind': 'newNote',
+      'item': 'japanese',
+      'version': 0,
+    });
+    expect(
+      (thread.json['proposed']! as Map<String, Object?>)['title'],
+      'Particles が',
+    );
+    // Nothing added; back at the studyset.
+    final notes = NoteRepository(noteGateway);
+    addTearDown(notes.dispose);
+    expect(await notes.notesOf('japanese'), hasLength(1));
+    expect(find.text('Suggest material'), findsOneWidget);
+  });
+
+  testWidgets("a Viewer's new flashcard goes as a suggestion; cancelled, "
+      'nothing goes and nothing is added', (tester) async {
+    await suggestNew(tester, 'Suggest a flashcard');
+    expect(
+      find.textContaining('suggesting something new', findRichText: true),
+      findsOneWidget,
+    );
+    await tester.tap(find.text('Cancel'));
+    await tester.pumpAndSettle();
+    expect(written.threads, isEmpty);
+    expect(find.text('Suggest material'), findsOneWidget);
+
+    await tester.tap(find.text('Suggest material'));
+    await tester.pumpAndSettle();
+    await tester.tap(find.text('Suggest a flashcard'));
+    await tester.pump();
+    await tester.pump(const Duration(seconds: 1));
+    await tester.pumpAndSettle();
+    await send(tester, 'A card on Kyoto.');
+
+    expect(written.threads.single.json['target'], {
+      'kind': 'newCard',
+      'item': 'japanese',
+      'version': 0,
+    });
+    final cards = CardRepository(cardGateway);
+    addTearDown(cards.dispose);
+    expect(await cards.cardsIn(['japanese']), hasLength(1));
+    expect(find.text('Suggest material'), findsOneWidget);
+  });
+
   testWidgets("a shared studyset's menu offers its suggestions", (
     tester,
   ) async {