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/sources/live/contract.test.mjs

@@ -313,3 +313,23 @@ test('identity lookup validates its response and honors body-parse cancellation'
     name: 'AbortError',
   });
 });
+
+test('transponder squawk and ADS-B emergency status are carried, blanks stay null', () => {
+  const squawking = [...aircraft, '7700'];
+  const civil = openSkySnapshot({ states: [squawking] }, { now }).records[0];
+  assert.equal(civil.squawk, '7700');
+  assert.equal(civil.emergency, null);
+  assert.equal(openSkySnapshot({ states: [aircraft] }).records[0].squawk, null);
+  const mil = normalizeReadsbAircraft(
+    { hex: 'abc123', lat: 30, lon: -97, squawk: '7600', emergency: 'NORDO' },
+    now,
+  );
+  assert.equal(mil.squawk, '7600');
+  assert.equal(mil.emergency, 'nordo');
+  const quiet = normalizeReadsbAircraft(
+    { hex: 'abc123', lat: 30, lon: -97 },
+    now,
+  );
+  assert.equal(quiet.squawk, null);
+  assert.equal(quiet.emergency, null);
+});