Disable YOLO training plot side effects

backend/tests/test_sprint129_operator_yolo_training_dataset.py

@@ -63,6 +63,7 @@ def test_operator_yolo_train_smoke_script_contract() -> None:
     assert "dataset.yaml" in script
     assert "from ultralytics import YOLO" in script
     assert "model.train" in script
+    assert "plots=False" in script
     assert "training_summary.json" in script
     assert "download" not in script.lower()
     assert "fixture_mode" not in script