Merge main (82022306) into fix/flights-unpositioned-rows-complete

Resolve conflicts with main by keeping both sides:
- CHANGELOG.md: keep this PR's flights entry above main's newer entries.
- src/layers/flights/records.test.mjs: keep this PR's position-less
  retention test alongside main's civil emergency-status test.

src/sources/live/aircraft.js merged cleanly: openSkySnapshot keeps main's
emergencyByIcao normalizer and passes openSkyUnpositionedId to admitRecords.

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

src/sources/live/contract.test.mjs

@@ -357,3 +357,23 @@ test('identity lookup validates its response and honors body-parse cancellation'
     name: 'AbortError',
   });
 });
+
+test('squawks are validated and omitted OpenSky status differs from an explicit ADS-B clear', () => {
+  const squawking = [...aircraft, '7700'];
+  const civil = openSkySnapshot({ states: [squawking] }, { now }).records[0];
+  assert.equal(civil.squawk, '7700');
+  assert.equal(civil.emergency, undefined);
+  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);
+});