fix: keep teacher runtime prompts within interface boundary

tests/unit/teacher-reply-history.test.ts

@@ -112,6 +112,40 @@ async function fixture(value: TeacherTopic) {
 }
 
 describe('passive teacher reply history compatibility', () => {
+  it('retains all four historical shortcuts through read, list and a later save', async () => {
+    const original = topic(archivedCases[4]);
+    const historicalReplies = [
+      '看懂规则｜摸头会改变什么？',
+      '想想作用｜我们聊聊摸头的作用。',
+      '试试结果｜怎样知道变化发生了？',
+      '换个话题｜我想先聊别的地方。',
+    ];
+    original.requests[0].suggestedQuestions = historicalReplies;
+    const f = await fixture(original);
+
+    const loaded = await f.store.read(original.id);
+    expect(loaded).toEqual(original);
+    expect(loaded.requests[0].suggestedQuestions).toEqual(historicalReplies);
+    expect((await f.store.list()).items).toEqual([{
+      id: original.id, title: original.requests[0].text, updatedAt: original.updatedAt,
+      version: 31, teacherId: 'selected-agent',
+    }]);
+    expect(await new TeacherTopicStore(f.root).read(original.id)).toEqual(original);
+    await f.unchanged();
+
+    loaded.revision++;
+    loaded.requests.push(request({ id: 'new-turn', presentation: 'reply-v1', suggestedQuestions: [],
+      discussionError: undefined, unparsedResponse: undefined }));
+    await f.store.save(loaded);
+    const expected = JSON.parse(JSON.stringify({ ...original,
+      revision: original.revision + 1, requests: [...original.requests, loaded.requests[1]],
+    }));
+    const saved = JSON.parse(await readFile(f.file, 'utf8'));
+    expect(saved).toEqual(expected);
+    expect(saved.requests[0].suggestedQuestions).toEqual(historicalReplies);
+    expect(await new TeacherTopicStore(f.root).read(original.id)).toEqual(expected);
+  });
+
   it.each(archivedCases)('keeps $name opaque through read, list and a later save', async archive => {
     const original = topic(archive);
     const f = await fixture(original);