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]>

src/layers/streetLevel/viewerHost.js

@@ -25,7 +25,7 @@ export function createViewerHost({ state, parts }) {
   }
 
   function applyPose(pose) {
-    if (!active || pose.providerId !== active.id) return;
+    if (!active || !state.street.open || pose.providerId !== active.id) return;
     const previousSequence = state.street.sequenceId;
     Object.assign(state.street, {
       providerId: pose.providerId,