feat(ui): 创建共享 UI 组件包

将 web 和 desktop 的重复代码抽取到 @ai-assistant/ui 包:

- 添加可配置的 API 客户端 (configureApiClient)
- 迁移共享组件: ChatMessage, ChatInput, Sidebar, FileBrowser, ConfigPanel
- 迁移共享 hook: useChat
- 添加 responsive prop 支持响应式布局
- 更新 web/desktop 依赖并删除重复代码

packages/ui/package.json

@@ -0,0 +1,33 @@
+{
+  "name": "@ai-assistant/ui",
+  "version": "1.0.0",
+  "description": "AI Terminal Assistant Shared UI Components",
+  "type": "module",
+  "main": "dist/index.js",
+  "types": "dist/index.d.ts",
+  "exports": {
+    ".": {
+      "import": "./dist/index.js",
+      "types": "./dist/index.d.ts"
+    },
+    "./styles": "./src/styles/index.css"
+  },
+  "scripts": {
+    "build": "tsc",
+    "dev": "tsc --watch",
+    "typecheck": "tsc --noEmit"
+  },
+  "peerDependencies": {
+    "react": "^18.0.0",
+    "react-dom": "^18.0.0"
+  },
+  "dependencies": {
+    "clsx": "^2.1.0",
+    "lucide-react": "^0.344.0"
+  },
+  "devDependencies": {
+    "@types/react": "^18.3.0",
+    "@types/react-dom": "^18.3.0",
+    "typescript": "^5.3.3"
+  }
+}