refactor(street-level): one provider, no orbit overview, no prewarm, simpler tile choice

The layer now owns its Mapillary parts directly: the provider registry,
pick router, multi-provider UI summary, params codec helper and provider
context are gone. createStreetLevelLayer({ source }) builds coverage,
sequences, the nearest-image lookup and the MapillaryJS viewer itself; a
single providerOn switch keeps the share link's `mapillary` option (off
draws nothing), and getParams/setParams keep { mapillary, pano, sinceDays }.

No z0-5 overview points: above 60 km nothing is drawn and the panel says to
zoom in; the proxy now serves only coverage z11-14. Tiles come from the
visible ground within range of the camera, ranked from the ground under it
(no line-of-sight ranking or near-range padding). MapillaryJS loads on the
first photo; viewer prewarm is removed. Key status, a rejected key and a
rate limit share one `blocked` state on coverage.

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

src/ui/streetLevelPresentation.js

@@ -67,13 +67,10 @@ function presentStatus(state) {
     : { text: 'OFF', tone: '', pressed, title };
 }
 
-/** How to add the missing key, for the provider that needs one. */
-function keyHint(state) {
-  const provider = (state.providers || []).find(
-    (entry) => entry.keyRequired === true && entry.requiresKeyId,
-  );
-  const requirement = provider && keySetupRequirement(provider.requiresKeyId);
-  return requirement ? `${provider.name}: ${requirement}` : null;
+/** How to add the missing Mapillary key. */
+function keyHint() {
+  const requirement = keySetupRequirement('mapillary');
+  return requirement ? `Mapillary: ${requirement}` : null;
 }
 
 function presentViewer(state) {
@@ -90,7 +87,7 @@ function presentViewer(state) {
     captionLeft: street.creator ? `Image by ${street.creator}` : '',
     captionRight: right.join(' · '),
     link: street.externalUrl || null,
-    linkLabel: street.providerLabel ? `${street.providerLabel} ↗` : '',
+    linkLabel: street.externalUrl ? 'MAPILLARY ↗' : '',
   };
 }
 
@@ -115,7 +112,7 @@ export function presentStreetLevelPanel(state, { now = Date.now() } = {}) {
     status: presentStatus(state),
     controlsDisabled: state.keyRequired === true,
     error: keyMissing
-      ? keyHint(state)
+      ? keyHint()
       : state.street.error || state.coverage.error || null,
     filter: { pano: filter.pano, sinceDays: Number(filter.sinceDays) || 0 },
     since: presentSince(filter.sinceDays, now),