fix(drone-airspace): show stale FAA snapshots as stale and cap them at a day

The source dropped the proxy's stale flag and fetch time, so the layer row
read nominal and freshly updated through an outage, and the proxy served its
last snapshot indefinitely. Carry stale and fetchedAt through the source as
Fire Perimeters does, date a stale snapshot by its fetch, and stop serving a
snapshot more than 24 hours old.

src/layers/droneAirspace/index.js

@@ -42,6 +42,7 @@ export function createDroneAirspaceLayer({
   let _count = 0;
   let _lastUpdate = null;
   let _lastError = null;
+  let _stale = false;
   let _enabled = false;
   let _clickHandler = null;
   let _selectedId = null;
@@ -153,6 +154,7 @@ export function createDroneAirspaceLayer({
       _count = 0;
       _lastUpdate = null;
       _lastError = null;
+      _stale = false;
       _enabled = false;
       console.log('[Data:DroneAirspace] Initialized');
     },
@@ -179,9 +181,21 @@ export function createDroneAirspaceLayer({
       const request = new AbortController();
       _request = request;
       try {
-        const rows = await source.getSnapshot({ signal: request.signal });
+        // The source contract is getSnapshot; a source that can also say how
+        // fresh its rows are (the FAA proxy) offers getSnapshotDetail.
+        const snapshot =
+          typeof source.getSnapshotDetail === 'function'
+            ? await source.getSnapshotDetail({ signal: request.signal })
+            : { rows: await source.getSnapshot({ signal: request.signal }) };
         if (request.signal.aborted || _request !== request || !_enabled)
           return false;
+        const { rows } = snapshot;
+        _stale = snapshot.stale === true;
+        // A stale snapshot is as old as its fetch, not this poll.
+        const updatedAt =
+          _stale && Number.isFinite(snapshot.fetchedAt)
+            ? snapshot.fetchedAt
+            : Date.now();
 
         const signature = JSON.stringify(
           rows
@@ -190,7 +204,7 @@ export function createDroneAirspaceLayer({
         );
         if (signature === _snapshotSignature) {
           if (_selectedId) publishSelectedCard();
-          _lastUpdate = Date.now();
+          _lastUpdate = updatedAt;
           _lastError = null;
           return true;
         }
@@ -239,7 +253,7 @@ export function createDroneAirspaceLayer({
         _snapshotSignature = signature;
         if (_selectedId) publishSelectedCard();
         _count = rows.length;
-        _lastUpdate = Date.now();
+        _lastUpdate = updatedAt;
         _lastError = null;
         console.log(
           `[Data:DroneAirspace] Updated: ${_count} zones, ${nextEntities.length} polygons`,
@@ -251,6 +265,8 @@ export function createDroneAirspaceLayer({
         console.warn('[Data:DroneAirspace] Fetch error:', e);
         _lastError =
           e?.message || msg('Restricted airspace source unavailable');
+        // A failure now outranks the stale snapshot still drawn.
+        _stale = false;
         return false;
       } finally {
         if (_request === request) _request = null;
@@ -273,6 +289,7 @@ export function createDroneAirspaceLayer({
       _count = 0;
       _lastUpdate = null;
       _lastError = null;
+      _stale = false;
     },
 
     getAnalystRecords(maxCount = 2000) {
@@ -322,6 +339,7 @@ export function createDroneAirspaceLayer({
         count: _count,
         lastUpdate: _lastUpdate,
         error: _lastError,
+        stale: _stale,
       };
     },
   };