feat(layers): highlight aircraft broadcasting a transponder emergency

Flights and Military Flights tint aircraft red while the latest poll
carries squawk 7500/7600/7700 or an adsb.lol ADS-B emergency status
(general/unlawful/nordo/downed). Minimum-fuel and lifeguard priorities
are reported but not tinted. The Cockpit HUD aircraft-meta line names
the broadcast code in red. The status is not sticky: a cleared code
stops highlighting on the next refresh.

The analyst/voice query engine gains squawk, emergency and
emergencyKind fields. No new source or request: OpenSky state vectors
already carry the squawk and adsb.lol/readsb carries both fields.

Built by the Hex project (Crew Leo Agile dev team).

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

CHANGELOG.md

@@ -95,6 +95,17 @@
 
 ## [Unreleased]
 
+- Flights and Military Flights highlight aircraft broadcasting a transponder
+  emergency. Squawk 7500 (unlawful interference), 7600 (radio failure) and
+  7700 (general emergency) — or adsb.lol's ADS-B `emergency` status, which
+  also reports downed aircraft — tint the aircraft red on the globe, in
+  Cockpit contacts and in snapshots, and name the code on the Cockpit HUD.
+  Minimum-fuel and lifeguard statuses are reported but not tinted. The status
+  follows the latest poll instead of sticking, so a cleared code stops
+  highlighting on the next refresh. The analyst and voice query engine can
+  filter by `squawk`, `emergency` and `emergencyKind`. No new source or
+  request: OpenSky already carries the squawk and adsb.lol carries both.
+
 - Street Level: Google Street View is the second provider. On the Google 3D
   map (Google's terms keep it off other maps), light its chip (off by
   default: every panorama is billed to the Google Maps key, which needs the