Warn when configured LLM is not frontier-recommended (#586)

Co-authored-by: Ahmed Allam <ahmed39652003@gmail.com>

strix/runtime/docker_client.py

@@ -49,7 +49,7 @@ logger = logging.getLogger(__name__)
 class StrixDockerSandboxClient(DockerSandboxClient):
     # Host directories to bind-mount into the container, set by the docker
     # backend before ``create()``. Each item is ``{source, target, read_only}``.
-    strix_bind_mounts: list[dict[str, Any]] = []  # overridden per-instance in backends.py
+    strix_bind_mounts: list[dict[str, Any]] | None = None
 
     async def _create_container(
         self,