frontend: add lazy server tree and folder items list with synced navigation and local state badges

Co-authored-by: Cursor <cursoragent@cursor.com>

mactfsui/app/lib/electron/bridge.ts

@@ -74,6 +74,17 @@ export async function selectDirectory(): Promise<string | null> {
   return bridge.selectDirectory()
 }
 
+/**
+ * 批量检测本地绝对路径是否存在，非 Electron 环境返回 null 表示无法检测。
+ */
+export async function pathsExist(paths: string[]): Promise<Record<string, boolean> | null> {
+  const bridge = getBridge()
+  if (!bridge || paths.length === 0) {
+    return bridge ? {} : null
+  }
+  return bridge.pathsExist(paths)
+}
+
 /**
  * 构造非 Electron 环境下的占位服务状态。
  */