harden delivery pipeline and production runtime

tests/ml/test_training.py

@@ -3,7 +3,7 @@ from __future__ import annotations
 import pytest
 
 from app.ml.feature_store import FeatureStore, FeatureVector
-from app.ml.training import TrainingPipeline, TrainedArtifact
+from app.ml.training import TrainingPipeline
 
 
 def _vector(sensor_id: str, temperature: float, label: str | None = None) -> FeatureVector:
@@ -45,4 +45,4 @@ def test_export_returns_registered_artifact() -> None:
 def test_export_missing_artifact_raises_key_error() -> None:
     pipeline = store_with_data()
     with pytest.raises(KeyError):
-        pipeline.export("artifact_v1")
+        pipeline.export("artifact_v1")