Check whether a backend class's execute accepts a timeout kwarg.
Older backend packages didn't lower-bound their SDK dependency, so they
may not accept the timeout keyword added to
SandboxBackendProtocol.
Results are cached per class to avoid repeated introspection overhead.
Composite backend that routes file operations by path prefix.
Routes operations to different backends based on path prefixes. Use this when you need different storage strategies for different paths (e.g., state for temp files, persistent store for memories).