test(executors): add future annotations import to edge case test file

为测试文件添加from __future__ import annotations以支持更规范的类型注解写法

tests/test_executors_edge_cases.py

@@ -1,5 +1,7 @@
 """Tests for executors module edge cases."""
 
+from __future__ import annotations
+
 import asyncio
 import logging
 import sys