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>

tests/test_coordinator.py

@@ -524,3 +524,18 @@ class BoundaryTests(unittest.IsolatedAsyncioTestCase):
         self.c._store.async_load.return_value = {'retired_learners': retired}
         await self.c.async_restore_model()
         self.assertEqual(list(self.c._retired), [f'sensor.old{i}' for i in range(6, 30)])
+
+    async def test_report_gap_maximum_is_exposed_per_sensor(self):
+        await self.sample(2400)  # the room then stays silent for 40 minutes
+        self.states['sensor.outside'].last_reported = self.now
+        data = await self.sample()
+        room = data['input_quality']['rooms']['sensor.room']
+        self.assertEqual((room['status'], room['max_age_seconds_24h']), ('stale', 2400))
+        self.states['sensor.room'].last_reported = self.now
+        self.states['sensor.outside'].last_reported = self.now
+        data = await self.sample()
+        room = data['input_quality']['rooms']['sensor.room']
+        self.assertEqual((room['status'], room['age_seconds'], room['max_age_seconds_24h']),
+                         ('valid', 0, 2400))
+        weather = data['input_quality']['weather']['temperature']['sensor.outside']
+        self.assertEqual(weather['max_age_seconds_24h'], 0)  # kept reporting; tracked separately