test(fires): pin the 47.5-hour flip to days and name where the age shows

Co-Authored-By: Claude Opus 5.5 <[email protected]>

docs/CURRENT-STATE.md

@@ -2382,7 +2382,7 @@ reporting are unchanged.
 ## FIRMS source status
 
 The FIRMS CSV parser rejects impossible acquisition calendar dates before the proxy filters records to the trailing 24 hours, while retaining valid UTC acquisition times.
-FIRMS ages round to whole hours before choosing a unit, so a 47.6-hour age reads "2d", not "48h".
+FIRMS ages round to whole hours before choosing a unit, so a 47.6-hour age reads "2d", not "48h"; with detections filtered to 24 hours, this shows mostly in the `STALE · cached {age}` stats line.
 The `get_active_fires` tool reports acquisition times as UTC ISO timestamps,
 including zero-padded hours and minutes; missing or invalid dates and times
 remain `null`, including impossible calendar dates from a custom source.