BEHAVIOR-003: learn causal shadow triggers

tests/ha/test_ha_reader.py

@@ -15,6 +15,7 @@ class FakeHaClient(HaClient):
             {
                 "entity_id": "sensor.temperature",
                 "state": "21.5",
+                "last_changed": "2026-06-14T12:00:00+00:00",
                 "attributes": {
                     "state_class": "measurement",
                     "device_class": "temperature",
@@ -87,6 +88,7 @@ def test_ha_reader_returns_summaries() -> None:
     sensor = next(item for item in summaries if item.entity_id == "sensor.temperature")
     assert sensor.unit_of_measurement == "°C"
     assert sensor.state == "21.5"
+    assert sensor.last_changed == datetime(2026, 6, 14, 12, 0, tzinfo=timezone.utc)
     assert sensor.area_name == "Kueche"
     assert sensor.device_name == "Thermometer"