feat(teacher): stream Yuxi reasoning and answer previews

tests/unit/coding-teacher.test.ts

@@ -1633,3 +1633,36 @@ describe('project consultations with selected cloud teachers', () => {
     await vi.waitFor(async () => expect((await f.service.read(scope, topic.id)).requests[0].status).toBe('completed'));
   });
 });
+
+it.each(['completed', 'cancelled'] as const)('persists streamed reasoning and prose separately when %s', async terminal => {
+  const f = await fixture({ cloudTeacher: true, mockCloud: true });
+  const scope = { ...f.scope, sourceId: 'project' };
+  const topic = await f.service.create(scope, undefined, undefined, 9);
+  f.replyWith(terminal === 'completed' ? '{"reply":"最终答案","quickReplies":["继续"]}' : '');
+  const requestId = crypto.randomUUID();
+  const seen: TeacherTopic[] = [];
+  const unsubscribe = await f.service.subscribe(scope, topic.id, next => seen.push(next));
+  await f.service.send(scope, topic.id, { requestId, text: '检查项目' });
+  const update = f.prepareCloud.mock.calls[0][8] as (value: { response?: string; reasoning?: string }) => void;
+  update({ reasoning: '先分析当前代码。' });
+  update({ response: '{"reply":"正在生成' });
+  const live = await f.service.read(scope, topic.id);
+  expect(live.requests[0]).toMatchObject({ status: 'running', reasoning: '先分析当前代码。', response: '正在生成' });
+  expect(seen.at(-1)!.requests[0].response).toBe('正在生成');
+  update({ response: '' });
+  expect((await f.service.read(scope, topic.id)).requests[0].response).toBe('');
+  update({ response: '{"reply":"新的正文' });
+  if (terminal === 'cancelled') await f.service.cancel(scope, topic.id, requestId);
+  else f.finish();
+  await vi.waitFor(async () => expect((await f.service.read(scope, topic.id)).requests[0].status).toBe(terminal));
+  unsubscribe();
+  const restarted = await f.restart();
+  const saved = (await restarted.read(scope, topic.id)).requests[0];
+  expect(saved.reasoning).toBe('先分析当前代码。');
+  expect(saved.response).toBe(terminal === 'completed' ? '最终答案' : '新的正文');
+  if (terminal === 'cancelled') expect(saved.unparsedResponse).toBe('{"reply":"新的正文');
+  const nextId = crypto.randomUUID();
+  await restarted.send(scope, topic.id, { requestId: nextId, text: '接着解释' });
+  expect(JSON.stringify(f.run.mock.calls.at(-1)![0])).not.toContain('先分析当前代码。');
+  await restarted.cancel(scope, topic.id, nextId);
+});