feat(teacher): stream Yuxi reasoning and answer previews

tests/unit/teacher-conversation-panel.test.tsx

@@ -180,3 +180,28 @@ describe('continuous agent panel', () => {
     expect(api.sendConversation).not.toHaveBeenCalled();
   });
 });
+
+it.each([undefined, 'suggestions'] as const)('updates reasoning and answer independently before completion (%s)', async intent => {
+  let current = topic([{ ...request('streaming'), intent, presentation: 'reply-v1', status: 'running', response: '' }]);
+  api.conversation.mockResolvedValue({ topic: current, before: null });
+  api.seenConversation.mockImplementation(async () => current);
+  await mount();
+  await waitFor(() => expect(api.events).toHaveBeenCalled());
+  const emit = async (patch: Partial<TeacherRequest>) => {
+    current = { ...current, revision: current.revision + 1, requests: [{ ...current.requests[0], ...patch }] };
+    await act(async () => stream.dispatchEvent(new MessageEvent('snapshot', { data: JSON.stringify(current) })));
+  };
+  await emit({ reasoning: '先读项目。' });
+  expect(screen.getByTestId('teacher-reasoning')).toHaveAttribute('open');
+  expect(screen.getByLabelText('智能体思考过程')).toHaveTextContent('先读项目。');
+  await emit({ reasoning: '先读项目。再分析玩法。', response: '正在生成正文' });
+  expect(screen.getByTestId('teacher-reply')).toHaveTextContent('正在生成正文');
+  expect(screen.getByTestId('teacher-reply')).not.toHaveTextContent('再分析玩法');
+  expect(screen.getByRole('button', { name: '停止回复' })).toBeEnabled();
+  await emit({ status: 'completed', response: '完整正文', suggestedQuestions: ['再讲一个例子'] });
+  expect(screen.getByTestId('teacher-reasoning')).not.toHaveAttribute('open');
+  expect(screen.getByTestId('teacher-reply')).toHaveTextContent('完整正文');
+  expect(screen.getByRole('button', { name: '再讲一个例子' })).toBeEnabled();
+  fireEvent.click(screen.getByText('思考过程'));
+  expect(screen.getByLabelText('智能体思考过程')).toHaveTextContent('再分析玩法。');
+});