refactor : 移除 -> None 返回值标注，拆分 FSDP 参数，新增 mmap 数据集存储

- 删除所有 def 函数 -> None 返回值类型标注
- FSDPExecutor 参数从 **kwargs 拆为显式声明，None 值自动过滤
- 新增 MmapStorage (bin) 存储后端，基于 numpy.memmap 零拷贝加载
- 新增 save_bin/load_bin/json_to_bin 工具函数
- detect_format 支持 bin 格式自动检测

astrai/trainer/strategy.py

@@ -125,7 +125,7 @@ class StrategyFactory(BaseFactory["BaseStrategy"]):
     """
 
     @classmethod
-    def _validate_component(cls, strategy_cls: type) -> None:
+    def _validate_component(cls, strategy_cls: type):
         """Validate that the strategy class inherits from BaseStrategy."""
         if not issubclass(strategy_cls, BaseStrategy):
             raise TypeError(f"{strategy_cls.__name__} must inherit from BaseStrategy")