fix: 修正 typing-extensions 依赖条件为 python_version < '3.13'

task.py 在 Python < 3.13 时需要 typing_extensions 的 TypeVar
(PEP 696 default= 参数), 此前条件 < '3.10' 导致 3.10-3.12
环境 import 失败, ReadTheDocs (Python 3.11) 构建报
ModuleNotFoundError: No module named 'typing_extensions'.

pyproject.toml

@@ -14,7 +14,7 @@ classifiers = [
 dependencies = [
     "graphlib_backport >= 1.0.0; python_version < '3.9'",
     "pyyaml>=6.0.1",
-    "typing-extensions>=4.13.2; python_version < '3.10'",
+    "typing-extensions>=4.13.2; python_version < '3.13'",
 ]
 description = "Lightweight, type-safe DAG task scheduler with multi-strategy execution."
 keywords = ["async", "dag", "scheduler", "task", "workflow"]