ML-008: add statistical baseline model

Closes #19

tests/ml/test_training.py

@@ -27,6 +27,11 @@ def test_run_returns_trained_artifact() -> None:
     artifact = pipeline.run("artifact_v1")
     assert artifact.artifact_id == "artifact_v1"
     assert artifact.supported_sensors == ("sensor.bedroom", "sensor.kitchen")
+    kitchen = artifact.feature_models["sensor.kitchen"]["temperature"]
+    assert kitchen.sample_count == 2
+    assert kitchen.mean == 19.5
+    assert kitchen.slope == 1.0
+    assert kitchen.forecast() == 21.0
 
 
 def test_run_without_data_raises_value_error() -> None: