fix(web): 修复 useChat 无限请求问题

- 用 useRef 存储回调函数，避免依赖变化导致无限循环
- 添加 onSessionNotFound 回调，会话不存在时自动创建新会话
- 限制 WebSocket 重连次数为 5 次
- 添加 web:dev 快捷脚本

packages/web/src/App.tsx

@@ -4,7 +4,7 @@
  * 响应式布局：支持桌面端和移动端
  */
 
-import { useState, useEffect } from 'react';
+import { useState, useEffect, useCallback } from 'react';
 import { Sidebar } from './components/Sidebar';
 import { ChatPage } from './pages/Chat';
 import { FileBrowser } from './components/FileBrowser';
@@ -49,6 +49,16 @@ export function App() {
     setCurrentSessionId(session.id);
   };
 
+  // 会话不存在时自动创建新会话
+  const handleSessionNotFound = useCallback(async () => {
+    try {
+      const { data: newSession } = await createSession();
+      setCurrentSessionId(newSession.id);
+    } catch (error) {
+      console.error('Failed to create new session:', error);
+    }
+  }, []);
+
   if (isInitializing) {
     return (
       <div className="h-screen flex items-center justify-center bg-gray-900">
@@ -116,7 +126,7 @@ export function App() {
         {/* 聊天区域 */}
         <div className={`flex-1 min-w-0 ${showFileBrowser ? 'hidden md:block md:w-1/2' : 'w-full'}`}>
           {currentSessionId ? (
-            <ChatPage key={currentSessionId} sessionId={currentSessionId} />
+            <ChatPage key={currentSessionId} sessionId={currentSessionId} onSessionNotFound={handleSessionNotFound} />
           ) : (
             <div className="flex-1 flex items-center justify-center h-full">
               <p className="text-gray-400">Select or create a session</p>