feat(squawk): carry emergencySource + observation time into analyst records

Review on #856 (kvnloo): the analyst projection flattened a 7700 squawk and
the readsb ADS-B emergency field into the same emergency/emergencyKind pair.

- mapAnalystRecord (flights, military) adds emergencySource ('squawk' |
  'ads-b' | null, from aircraftEmergency().source), emergencyBroadcast (new
  pure emergencyBroadcastPhrase: "broadcasting squawk 7700 (general
  emergency)" vs "ADS-B reports general emergency") and observedAtMs (the
  record's lastContactEpochMs: last transponder message, epoch ms).
- emergencySource is a queryable analyst text field; the voice payload passes
  it and emergencyBroadcast through, and observedAtMs only for aircraft with
  a status. Tool description asks the model to narrate with the phrase.
- Source-to-analyst fixture test: OpenSky 7700 vs adsb.lol emergency=general
  on squawk 1200 differ in provenance and timestamp; filterable by source.
- Voice tool-payload pins re-derived for the additive description change.

Co-Authored-By: Claude Opus 5.5 (1M context) <[email protected]>

src/data/aircraftEmergency.test.mjs

@@ -3,6 +3,7 @@ import { test } from 'node:test';
 import assert from 'node:assert/strict';
 import {
   aircraftEmergency,
+  emergencyBroadcastPhrase,
   isEmergency,
   normalizeSquawk,
 } from './aircraftEmergency.js';
@@ -62,3 +63,22 @@ test('priority statuses are reported but are not emergencies', () => {
   assert.equal(isEmergency(aircraftEmergency({ emergency: 'minfuel' })), false);
   assert.equal(isEmergency(null), false);
 });
+
+test('the broadcast phrase quotes a naming code, else attributes ADS-B', () => {
+  assert.equal(
+    emergencyBroadcastPhrase(aircraftEmergency({ squawk: '7700' })),
+    'broadcasting squawk 7700 (general emergency)',
+  );
+  assert.equal(
+    emergencyBroadcastPhrase(
+      aircraftEmergency({ squawk: '1200', emergency: 'general' }),
+    ),
+    'ADS-B reports general emergency',
+  );
+  assert.equal(
+    emergencyBroadcastPhrase(aircraftEmergency({ emergency: 'lifeguard' })),
+    'ADS-B reports lifeguard (medical priority)',
+  );
+  assert.equal(emergencyBroadcastPhrase(null), null);
+  assert.equal(emergencyBroadcastPhrase({ kind: 'reserved' }), null);
+});