fix(military): read a GNSS-sourced vertical rate when no baro rate is sent

readsb reports an aircraft's vertical rate as geom_rate instead of baro_rate
when its source is GNSS. The military normaliser read only baro_rate, so about
one in six live /v2/mil contacts had a null vertical rate in analyst and
tracked-aircraft data. Fall back to geom_rate, as the adsb.lol flights
fallback already does; a sent baro_rate still wins.

src/sources/live/aircraft.js

@@ -48,7 +48,8 @@ export function normalizeReadsbAircraft(row, snapshotTimeMs) {
   const baroFt = finite(row.alt_baro),
     geoFt = finite(row.alt_geom);
   const speedKts = finite(row.gs),
-    rateFtMin = finite(row.baro_rate);
+    // readsb sends a GNSS-sourced rate as geom_rate instead of baro_rate.
+    rateFtMin = finite(row.baro_rate) ?? finite(row.geom_rate);
   const seen = finite(row.seen),
     seenPos = finite(row.seen_pos);
   return {

src/sources/live/contract.test.mjs

@@ -145,6 +145,20 @@ test('readsb units and position/contact ages are normalized once against the sou
   );
 });
 
+test('readsb vertical rate falls back to the GNSS rate when no baro rate is sent', () => {
+  // readsb reports the rate under geom_rate when the aircraft's source is
+  // GNSS; 26 of 157 positioned rows in a live /v2/mil fetch had only that.
+  const row = { hex: 'ae638d', lat: 20.3, lon: -158.5, geom_rate: -2432 };
+  assert.equal(
+    normalizeReadsbAircraft(row, now).verticalRateMps,
+    -2432 * 0.00508,
+  );
+  assert.equal(
+    normalizeReadsbAircraft({ ...row, baro_rate: -2400 }, now).verticalRateMps,
+    -2400 * 0.00508,
+  );
+});
+
 test('vessel identity, opaque reference and heading/course remain distinct, unknowns stay null', () => {
   const row = normalizeVesselObservation(
     {