Show each sensor's longest report gap; stop recording volatile attributes

Choosing room and weather freshness limits required knowing how long
each sensor normally goes without reporting, which HA does not show.
Add max_age_seconds_24h to every source in input_quality: the largest
report age seen at polls over the last 24 hours (hourly buckets, reset
on reload, underestimates by up to one poll interval).

input_quality and weather_comparison change every poll, so the Recorder
stored a new attribute row every five minutes. Mark them unrecorded;
they remain visible on the Status entity. Model coefficients and other
attributes are still recorded.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

custom_components/heating_mpc/sensor.py

@@ -19,6 +19,9 @@ class MPCStatus(CoordinatorEntity, SensorEntity):
     _attr_has_entity_name = True
     _attr_name = "Heating MPC Status"
     _attr_icon = "mdi:brain"
+    # Per-source report ages change every poll; recording them adds a new
+    # attribute row to the database every five minutes. Current values stay visible.
+    _unrecorded_attributes = frozenset({"input_quality", "weather_comparison"})
 
     def __init__(self, coordinator, entry_id):
         super().__init__(coordinator)