fix(street-level): settle loading on pan, keep zoom 0, drop late poses

Fixes from gekh's re-review of 061d269, each with a regression test that
fails on the old code:

- A pan that drops a tile still loading now settles the loading count
  (the aborted request no longer owns its key, so its `finally` never
  did), and purges the previous zoom's tiles once nothing is pending.
  LOADING no longer sticks on the status pill and chip.
- Zoom 0 (above 15,000 km) is a zoom: `zoom == null` instead of `!zoom`.
- A pose that arrives after a photo was closed is dropped, in the
  MapillaryJS adapter and in the viewer host, so the marker and sequence
  selection do not come back.
- Ground casting passes the tile's signal to the terrain request, so a
  cancelled tile stops its height batch instead of holding the queue.
- The server's in-memory tile cache honours the 24 h TTL like the disk.
- The viewer's one-time resize runs for every photo, not just the first.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

server/providers/mapillary/tiles.js

@@ -77,6 +77,13 @@ const _inFlight = new Map();
 function memoryGet(key) {
   const hit = _memory.get(key);
   if (!hit) return null;
+  // Same 24 h life as the disk copy: a long-running server must not keep
+  // serving stale (or empty) coverage until eviction.
+  if (Date.now() - hit.at > TILE_DISK_TTL_MS) {
+    _memory.delete(key);
+    _memoryBytes -= hit.bytes.length;
+    return null;
+  }
   // Re-insert to mark as most recently used.
   _memory.delete(key);
   _memory.set(key, hit);