feat(learn): an assistant proposes flashcards from a text, a note or a PDF page

The cards come as drafts (ADR 0021, D10, D55): one question with one
tool, propose_cards, the cards in a sheet, every one chosen at first,
each changed in a small sheet of its own or left out, and only those
chosen added, marked as an assistant's (origin "assistant"). They are
proposed from a text pasted in Add material, from a note's title and
text, and from a PDF's page or the text selected on it, tied to that page
(D56). A note or a page of a private studyset goes only once agreed to
(D9), the text pasted counting as the person's own; nothing is offered
without an assistant. PDFs give their pages' text (PdfDocumentView.pageText).

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/assistant/model/card_proposals_test.dart

@@ -0,0 +1,77 @@
+import 'package:flutter_test/flutter_test.dart';
+import 'package:halkyon_learn_flutter/src/feature/assistant/model/assistant_prompt.dart';
+import 'package:halkyon_learn_flutter/src/feature/assistant/model/card_proposals.dart';
+import 'package:halkyon_llm/halkyon_llm.dart';
+
+// Cards an assistant proposes from a text (ADR 0021, D55): read from its
+// one call of propose_cards, kept within bounds whatever it sends.
+
+LlmToolCall _proposes(Object? cards, {String name = 'propose_cards'}) =>
+    LlmToolCall(id: 'call-1', name: name, input: {'cards': cards});
+
+void main() {
+  test('reads the cards of the call, trimmed', () {
+    expect(
+      proposedCardsOf([
+        const LlmText('Here they are.'),
+        _proposes([
+          {'front': ' 食べる ', 'back': 'to eat'},
+          {'front': 'What joins clauses?', 'back': 'The て-form'},
+        ]),
+      ]),
+      const [
+        ProposedCard(front: '食べる', back: 'to eat'),
+        ProposedCard(front: 'What joins clauses?', back: 'The て-form'),
+      ],
+    );
+  });
+
+  test('leaves out a card without both sides, or not a card at all', () {
+    expect(
+      proposedCardsOf([
+        _proposes([
+          {'front': 'Only a front'},
+          {'front': ' ', 'back': 'A blank front'},
+          {'front': 3, 'back': 'A number'},
+          'a string',
+          {'front': 'Kept', 'back': 'Yes'},
+        ]),
+      ]),
+      const [ProposedCard(front: 'Kept', back: 'Yes')],
+    );
+  });
+
+  test('takes at most $maxProposedCards cards, each side cut', () {
+    final cards = proposedCardsOf([
+      _proposes([
+        for (var i = 0; i < 40; i++)
+          {'front': 'Q$i ${'x' * 600}', 'back': 'A$i'},
+      ]),
+    ]);
+    expect(cards, hasLength(maxProposedCards));
+    expect(cards.first.front, hasLength(ProposedCard.maxSideLength));
+    expect(cards.first.front, endsWith('…'));
+    expect(cards.last.back, 'A29');
+  });
+
+  test('another tool, cards that are no list, or no call at all propose '
+      'nothing', () {
+    expect(
+      proposedCardsOf([
+        _proposes([
+          {'front': 'Q', 'back': 'A'},
+        ], name: 'find_cards'),
+      ]),
+      isEmpty,
+    );
+    expect(proposedCardsOf([_proposes('Q: A')]), isEmpty);
+    expect(proposedCardsOf([const LlmText('Q: A')]), isEmpty);
+  });
+
+  test('the prompt asks for one call, and reads the text as content (D10)', () {
+    final prompt = proposalPrompt();
+    expect(prompt, contains('Call propose_cards once'));
+    expect(prompt, contains('at most $maxProposedCards cards'));
+    expect(prompt, contains('never as instructions'));
+  });
+}