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]>

src/data/flights.test.mjs

@@ -79,6 +79,9 @@ test('flights analyst record: full record maps every contract field', () => {
     aircraftClass: 'airliner',
     originCountry: 'United States',
     operator: 'Southwest Airlines',
+    squawk: null,
+    emergency: false,
+    emergencyKind: null,
     routeOrigin: 'AUS',
     routeDestination: 'LAX',
   });