fix(tree): move Iterable import into type-checking block

app/tree/environment.py

@@ -11,7 +11,6 @@ from __future__ import annotations
 
 import re
 from pathlib import Path
-from collections.abc import Iterable
 from typing import TYPE_CHECKING, Any
 
 import numpy as np
@@ -20,7 +19,7 @@ from loguru import logger
 from app.tree.index import L1Node, L2Node, L3Node, TreeIndex
 
 if TYPE_CHECKING:
-    from collections.abc import Callable
+    from collections.abc import Callable, Iterable
 
 # 节点联合类型（内部使用）
 AnyNode = L1Node | L2Node | L3Node