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/ui/package.json

@@ -22,6 +22,13 @@
     "react-dom": "^18.0.0"
   },
   "dependencies": {
+    "@codemirror/lang-css": "^6.3.1",
+    "@codemirror/lang-html": "^6.4.11",
+    "@codemirror/lang-javascript": "^6.2.4",
+    "@codemirror/lang-json": "^6.0.2",
+    "@codemirror/lang-markdown": "^6.5.0",
+    "@codemirror/lang-python": "^6.2.1",
+    "@codemirror/theme-one-dark": "^6.1.3",
     "@radix-ui/react-dialog": "^1.1.15",
     "@radix-ui/react-dropdown-menu": "^2.1.16",
     "@radix-ui/react-popover": "^1.1.15",
@@ -29,6 +36,7 @@
     "@radix-ui/react-slider": "^1.3.6",
     "@radix-ui/react-switch": "^1.2.6",
     "@radix-ui/react-tooltip": "^1.2.8",
+    "@uiw/react-codemirror": "^4.25.4",
     "class-variance-authority": "^0.7.1",
     "clsx": "^2.1.1",
     "framer-motion": "^12.23.26",