fix(chat): reconcile reply recovery with continuous agent conversations

tests/e2e/fixtures/teacher-reply-layout.tsx

@@ -1,13 +1,15 @@
 import { createRoot } from 'react-dom/client';
+import { fixtureAgent } from './teacher-reply-api';
 import { TeacherChatPanel } from '../../../src/pages/Chat/TeacherChatPanel';
 import '../../../src/styles/globals.css';
 import '../../../src/pages/Chat/classroom-workspace.css';
 import 'katex/dist/katex.min.css';
+const continuous = new URLSearchParams(location.search).get('chat') === 'continuous';
 const width = Number(new URLSearchParams(location.search).get('width')) || 508;
 createRoot(document.getElementById('root')!).render(<div className="classroom-workspace flex h-screen flex-col bg-white">
   <header className="flex h-10 shrink-0 items-center border-b px-5 text-xs">智能体回复交互测试 · 真实页面组件 / 模拟回复</header>
   <div className="flex min-h-0 flex-1 justify-end bg-[#f5f5f1]">
     <main className="min-w-0 flex-1 p-8"><h1 className="text-lg">我的小狗世界</h1><p className="mt-4 text-sm text-muted-foreground">作品区域</p></main>
-    <div className="h-full shrink-0 border-l" style={{ width }}><TeacherChatPanel projectId="fixture" sourceId="source" /></div>
+    <div className="h-full shrink-0 border-l" style={{ width }}><TeacherChatPanel projectId="fixture" sourceId={continuous ? 'original-source' : 'source'} selectedAgent={continuous ? fixtureAgent : undefined} /></div>
   </div>
 </div>);