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.test.mjs

@@ -27,17 +27,22 @@ function fakeAdapter({ failMounts = 0 } = {}) {
       calls.mount++;
       if (calls.mount <= failMounts) throw new Error('library failed to load');
     },
-    async open(id) {
-      calls.open.push(id);
+    /** A pose event from the library, as MapillaryJS fires them. */
+    emitPose(id) {
       emit?.({
         providerId: 'mapillary',
         imageId: id,
+        sequenceId: `seq-${id}`,
         position: { lon: 1, lat: 2 },
         bearing: 90,
         isPano: false,
         externalUrl: `https://example.test/${id}`,
       });
     },
+    async open(id) {
+      calls.open.push(id);
+      this.emitPose(id);
+    },
     close() {},
     unmount() {
       calls.unmount++;
@@ -127,3 +132,17 @@ test('switching one provider off releases only its viewer', async () => {
   host.unmount('mapillary');
   assert.equal(adapter.calls.unmount, 1);
 });
+
+test('a pose that arrives after the photo was closed does not bring it back', async () => {
+  const adapter = fakeAdapter();
+  const { state, host } = harness(adapter);
+  await host.open('mapillary', 'a');
+  host.close();
+  const before = { ...state.street };
+  // The library's `image` event for a photo that was still loading.
+  adapter.emitPose('a');
+  assert.equal(state.street.open, false);
+  assert.equal(state.street.imageId, null);
+  assert.equal(state.street.sequenceId, null);
+  assert.deepEqual(state.street, before);
+});