fix(street-level): re-check an unknown key, Esc leaves full screen, say why a view is empty

- A failed or missing key status is asked again on the next switch-on, and
  the check gives up after 10 s instead of holding LOADING forever.
- Waiting for the key status reads as LOADING while the layer is on.
- Esc shrinks the photo in full screen too, before the panel's own Esc.
- Destroying the panel with the iPhone popover open leaves no popover behind.
- An empty view says whether the filter emptied it.
- A freed upstream tile slot passes straight to the oldest waiter.

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

src/ui/streetLevelPresentation.js

@@ -103,7 +103,14 @@ function presentMeta(state) {
       : `${state.sequence.images.toLocaleString()} images in this sequence · Esc clears`;
   if (state.coverage.count > 0)
     return `${state.coverage.count.toLocaleString()} sequences in view · click a line for its photos`;
-  return state.coverage.hint || '';
+  if (state.coverage.hint) return state.coverage.hint;
+  // Still loading, or the error line already says why.
+  if (state.coverage.loading || state.keyRequired || state.coverage.error)
+    return '';
+  const filter = state.filter || {};
+  return (filter.pano || 'all') !== 'all' || Number(filter.sinceDays) > 0
+    ? 'No sequences in view match the filter'
+    : 'No Mapillary coverage in view';
 }
 
 /** @param {{now?: number}} [options] Clock for the SINCE readout. */