tree: fix __root__ expansion returns subdirs

wwwroot/api/workspace_tree.dspy

@@ -43,8 +43,14 @@ if not node_id:
         "is_leaf": False
     }]
 
-# 展开节点
-scan_path = ws_dir + '/' + node_id
+# 展开节点：__root__ 特殊处理，其余用相对路径
+if node_id == '__root__':
+    scan_path = ws_dir
+    id_prefix = ''
+else:
+    scan_path = ws_dir + '/' + node_id
+    id_prefix = node_id + '/'
+
 if not os.path.isdir(scan_path):
     return []
 
@@ -60,7 +66,7 @@ for name in entries:
         continue
     if os.path.isdir(full):
         items.append({
-            "id": node_id + '/' + name,
+            "id": id_prefix + name,
             "parentid": node_id,
             "label": "📁 " + name,
             "path": full,