feat(ui): 添加编辑器和文件浏览器状态持久化

- FileExplorer: 保存展开的目录路径到 localStorage
- IDE: 保存打开的标签页和活动标签，刷新后自动恢复
- App: 调整 IDE 面板默认宽度为 70%

packages/ui/src/components/FileExplorer.tsx

@@ -132,11 +132,21 @@ function TreeNode({ node, depth, onFileSelect, expandedPaths, onToggleExpand }:
   );
 }
 
+const STORAGE_KEY_EXPANDED = 'ai-assistant-file-explorer-expanded';
+
 export function FileExplorer({ onFileSelect, className, workingDirectory }: FileExplorerProps) {
   const [tree, setTree] = useState<FileTreeNode[]>([]);
   const [loading, setLoading] = useState(true);
   const [error, setError] = useState<string | null>(null);
-  const [expandedPaths, setExpandedPaths] = useState<Set<string>>(new Set());
+  // 从 localStorage 恢复展开状态
+  const [expandedPaths, setExpandedPaths] = useState<Set<string>>(() => {
+    try {
+      const saved = localStorage.getItem(STORAGE_KEY_EXPANDED);
+      return saved ? new Set(JSON.parse(saved)) : new Set();
+    } catch {
+      return new Set();
+    }
+  });
 
   // 加载文件树
   const loadTree = useCallback(async () => {
@@ -146,13 +156,7 @@ export function FileExplorer({ onFileSelect, className, workingDirectory }: File
       const result = await getFileTree('.', 4);
       if (result.success) {
         setTree(result.data.tree);
-        // 默认展开第一层
-        const firstLevel = new Set(
-          result.data.tree
-            .filter((n) => n.type === 'directory')
-            .map((n) => n.path)
-        );
-        setExpandedPaths(firstLevel);
+        // 保持已保存的展开状态（不重置）
       } else {
         setError('Failed to load file tree');
       }
@@ -175,6 +179,8 @@ export function FileExplorer({ onFileSelect, className, workingDirectory }: File
       } else {
         next.add(path);
       }
+      // 保存到 localStorage
+      localStorage.setItem(STORAGE_KEY_EXPANDED, JSON.stringify([...next]));
       return next;
     });
   }, []);