Handoff completed training into closed loop

backend/tests/test_yolo_training_supervisor.py

@@ -28,3 +28,10 @@ def test_container_running_fails_closed_on_inspect_error(monkeypatch) -> None:
 
     monkeypatch.setattr(MODULE.subprocess, "run", lambda *args, **kwargs: Result())
     assert MODULE.container_running("missing") is False
+
+
+def test_completion_command_requires_non_empty_string_list(tmp_path: Path) -> None:
+    invalid = tmp_path / "command.json"
+    invalid.write_text('{"shell": "unsafe"}', encoding="utf-8")
+    value = MODULE.json.loads(invalid.read_text(encoding="utf-8"))
+    assert not isinstance(value, list)