"""Docker container-based sandbox backend. Phase 2 implementation.""" class DockerSandbox: async def execute(self, command: str, timeout: int = 300): raise NotImplementedError("Phase 2") async def read_file(self, path: str) -> str: raise NotImplementedError("Phase 2") async def write_file(self, path: str, content: str) -> None: raise NotImplementedError("Phase 2") async def close(self) -> None: raise NotImplementedError("Phase 2")