feat(ui): 添加 IDE 组件（文件浏览器 + 代码编辑器）

- 新增 CodeEditor 组件，基于 CodeMirror 实现多标签代码编辑
- 新增 FileExplorer 组件，支持文件树展开/折叠和文件选择
- 新增 IDE 组件，整合文件浏览器和代码编辑器
- 新增 SessionPanel 组件，用于会话管理
- 添加文件写入 API（PUT /api/files/write）
- 优化布局：IDE 始终显示，移除文件切换按钮
- 工作目录路径显示在文件浏览器标题栏，支持悬浮显示完整路径

packages/web/src/pages/Chat.tsx

@@ -3,7 +3,7 @@
  */
 
 import { useEffect, useRef } from 'react';
-import { WifiOff, MessageSquare, FolderOpen, Terminal, Plug, Zap, Bot, History, Server, Folder } from 'lucide-react';
+import { WifiOff, MessageSquare, Terminal, Plug, Zap, Bot, History, Server, MessagesSquare } from 'lucide-react';
 import { motion, AnimatePresence } from 'framer-motion';
 import { toast } from 'sonner';
 import {
@@ -23,8 +23,6 @@ interface ChatPageProps {
   onSessionUpdated?: (sessionId: string, name: string) => void;
   responsive?: boolean;
   // 工具栏按钮
-  showFileBrowser?: boolean;
-  onToggleFileBrowser?: () => void;
   onOpenCommands?: () => void;
   onOpenMCP?: () => void;
   onOpenHooks?: () => void;
@@ -33,8 +31,7 @@ interface ChatPageProps {
   onOpenProviders?: () => void;
   onOpenLSP?: () => void;
   onOpenDiagnostics?: () => void;
-  // Working Directory
-  workingDirectory?: string;
+  onOpenSessions?: () => void;
 }
 
 export function ChatPage({
@@ -42,8 +39,6 @@ export function ChatPage({
   onSessionNotFound,
   onSessionUpdated,
   responsive = false,
-  showFileBrowser,
-  onToggleFileBrowser,
   onOpenCommands,
   onOpenMCP,
   onOpenHooks,
@@ -52,7 +47,7 @@ export function ChatPage({
   onOpenProviders,
   onOpenLSP,
   onOpenDiagnostics,
-  workingDirectory,
+  onOpenSessions,
 }: ChatPageProps) {
   const {
     messages,
@@ -162,18 +157,7 @@ export function ChatPage({
     <div className="flex-1 flex flex-col h-screen">
       {/* Header */}
       <div className="flex items-center justify-between px-4 md:px-6 py-3 border-b border-line bg-surface-subtle">
-        <div className="flex items-center gap-3 min-w-0">
-          <h1 className="text-lg font-medium text-fg flex-shrink-0">Chat</h1>
-          {/* Working Directory */}
-          {workingDirectory && (
-            <div className="flex items-center gap-1.5 text-sm text-fg-muted min-w-0">
-              <Folder size={14} className="flex-shrink-0 text-fg-subtle" />
-              <span className="truncate font-mono text-xs" title={workingDirectory}>
-                {workingDirectory}
-              </span>
-            </div>
-          )}
-        </div>
+        <h1 className="text-lg font-medium text-fg">Chat</h1>
         <div className="flex items-center gap-3 flex-shrink-0">
           {/* 上下文使用情况 - 紧凑模式 */}
           {sessionId && (
@@ -189,7 +173,7 @@ export function ChatPage({
           <ConnectionStatus />
 
           {/* 工具栏按钮 */}
-          {(onToggleFileBrowser || onOpenCommands || onOpenMCP || onOpenHooks || onOpenAgents || onOpenCheckpoints || onOpenProviders || onOpenLSP || onOpenDiagnostics) && (
+          {(onOpenCommands || onOpenMCP || onOpenHooks || onOpenAgents || onOpenCheckpoints || onOpenProviders || onOpenLSP || onOpenDiagnostics || onOpenSessions) && (
             <div className="flex items-center gap-1.5 border-l border-line-muted pl-3">
               {/* LSP 诊断指示器 */}
               {(onOpenLSP || onOpenDiagnostics) && (
@@ -278,20 +262,16 @@ export function ChatPage({
                 </motion.button>
               )}
 
-              {/* 文件浏览器按钮 - 仅桌面端显示 */}
-              {onToggleFileBrowser && (
+              {/* Sessions 按钮 */}
+              {onOpenSessions && (
                 <motion.button
                   whileHover={{ scale: 1.1 }}
                   whileTap={{ scale: 0.9 }}
-                  onClick={onToggleFileBrowser}
-                  className={`hidden md:block p-1.5 rounded-lg transition-colors ${
-                    showFileBrowser
-                      ? 'text-blue-400 bg-blue-500/20'
-                      : 'text-fg-muted hover:text-fg-secondary hover:bg-surface-muted'
-                  }`}
-                  title={showFileBrowser ? 'Hide Files' : 'Show Files'}
+                  onClick={onOpenSessions}
+                  className="p-1.5 rounded-lg text-fg-muted hover:text-fg-secondary hover:bg-surface-muted transition-colors"
+                  title="Sessions"
                 >
-                  <FolderOpen size={20} />
+                  <MessagesSquare size={20} />
                 </motion.button>
               )}
             </div>