Add teacher microphone and per-question model selection

tests/unit/coding-teacher-cloud.test.ts

@@ -870,3 +870,19 @@ it('keeps only the cloud main-thread answer while advancing past child events on
   expect(transport.events).toHaveBeenCalledTimes(2);
   expect(streamUrls[1]).toContain('after_seq=2-0');
 });
+
+it('transmits the frozen per-question model while retaining the teacher version', async () => {
+  const f = await fixture();
+  f.topic.requests.push({ id: requestId, modelId: 'selected-model', teacherVersion: 9, text: '问题', references: [], status: 'running',
+    createdAt: 'now', sourceCapturedAt: 'now', sourceCursor: f.access.source.cursor,
+    includedSourceMessageIds: [], omittedMessages: 0, response: '' });
+  const transport: TeacherCloudTransport = {
+    json: vi.fn(async url => url === '/questions'
+      ? { request_id: requestId, run_id: 'run' } : { status: 'completed', output: '已回复' }),
+    events: vi.fn(),
+  };
+  const model = prepareCloudTeacher(f.account, f.topic, requestId, f.access, f.progress, f.saveRequest, transport);
+  await model.run([{ role: 'user', content: '问题' }], new AbortController().signal, vi.fn());
+  expect(transport.json).toHaveBeenCalledWith('/questions', expect.objectContaining({ model_id: 'selected-model', teacher_version: f.topic.version }), expect.anything());
+  expect(f.topic.definition.model.model_id).toBe('deepseek-flash');
+});