fix(local-adsb): show a decoder feed's GNSS-sourced vertical rate

dump1090-fa and readsb file an aircraft's vertical rate under geom_rate
instead of baro_rate when its source is GNSS. The decoder-feed adapter
read only baro_rate, so those aircraft showed "V/S —" on the Local ADS-B
card. It now falls back to geom_rate; a sent baro_rate still wins.

docs/CURRENT-STATE.md

@@ -6134,7 +6134,9 @@ Receivers publish one record shape from `src/sources/adsbRecords.js`
 `lastMessageAt`, `messageCount`, `rssiDbfs`, `band`, `source`). `band` is `1090` or `978`; `source` is
 `webusb` (browser SDR) or `feed` (decoder feed).
 `normalizeDump1090Aircraft(json, nowMs, { band })` maps a dump1090/readsb/
-skyaware978 `aircraft.json` document into the same records. Voice
+skyaware978 `aircraft.json` document into the same records; a row without
+`baro_rate` reads its vertical rate from `geom_rate`, where a GNSS-sourced rate
+is sent. Voice
 `set_layer_visibility` accepts `local-adsb` ("local ADS-B", "my receiver",
 "my antenna").
 

src/sources/adsbRecords.js

@@ -247,7 +247,9 @@ export function normalizeDump1090Aircraft(json, nowMs, { band = '1090' } = {}) {
       altitudeFt: altitude,
       groundSpeedKt: finiteOrNull(entry.gs),
       trackDeg: normalizeTrack(entry.track),
-      verticalRateFpm: finiteOrNull(entry.baro_rate),
+      // A GNSS-sourced rate is sent as geom_rate instead of baro_rate.
+      verticalRateFpm:
+        finiteOrNull(entry.baro_rate) ?? finiteOrNull(entry.geom_rate),
       lastPositionAt: hasPosition
         ? receivedAt - Math.max(0, seenPosS) * 1000
         : null,

src/sources/adsbRecords.test.mjs

@@ -169,6 +169,20 @@ test('a feed document names its band on every record', () => {
   assert.ok(uat.every((record) => record.source === 'feed'));
 });
 
+test('a decoder feed reads a GNSS-sourced vertical rate when no baro rate is sent', () => {
+  // dump1090-fa and readsb file a velocity message's rate under geom_rate
+  // instead of baro_rate when its source bit says GNSS.
+  const rate = (fields) =>
+    normalizeDump1090Aircraft(
+      { aircraft: [{ hex: 'abc123', seen: 1, ...fields }] },
+      10_000,
+    )[0].verticalRateFpm;
+  assert.equal(rate({ geom_rate: -832 }), -832);
+  assert.equal(rate({ baro_rate: -768, geom_rate: -832 }), -768);
+  assert.equal(rate({ baro_rate: 0, geom_rate: -832 }), 0);
+  assert.equal(rate({}), null);
+});
+
 function heard(overrides = {}) {
   return {
     icao: 'abc123',