fix(docker): gate cwd workspace mount behind config

Keep Docker sandboxes isolated by default. Add an explicit terminal.docker_mount_cwd_to_workspace opt-in, thread it through terminal/file environment creation, and document the security tradeoff and config.yaml workflow clearly.

tools/file_tools.py

@@ -140,6 +140,7 @@ def _get_file_ops(task_id: str = "default") -> ShellFileOperations:
                 container_config=container_config,
                 local_config=local_config,
                 task_id=task_id,
+                host_cwd=config.get("host_cwd"),
             )
 
             with _env_lock: