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.js

@@ -63,6 +63,22 @@ export function aircraftEmergency({ squawk, emergency } = {}) {
   };
 }
 
+/**
+ * How a summary may phrase the status without flattening it into an incident:
+ * quote the code when the Mode A squawk itself names the status, otherwise
+ * attribute it to the ADS-B emergency field.
+ * @param {{kind?: string, squawk?: string|null, source?: string}|null|undefined} status
+ * @returns {string|null} e.g. 'broadcasting squawk 7700 (general emergency)'
+ *   or 'ADS-B reports general emergency'; null when there is no status.
+ */
+export function emergencyBroadcastPhrase(status) {
+  if (!status || !Object.hasOwn(KINDS, status.kind)) return null;
+  const label = KINDS[status.kind].label.toLowerCase();
+  return status.source === 'squawk' && status.squawk
+    ? `broadcasting squawk ${status.squawk} (${label})`
+    : `ADS-B reports ${label}`;
+}
+
 /**
  * True when the aircraft is broadcasting an emergency (not a priority status).
  * @param {{severity?: string}|null|undefined} status