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/streetLevelControls.js

@@ -180,15 +180,10 @@ export class StreetLevelControls {
 
   async _toggleEnabled() {
     const enabled = this.actions.isEnabled?.() === true;
-    // The pill is the only switch: switching on also brings back a provider
-    // a share link or a tool turned off, or the layer would draw nothing.
-    const dark = enabled
-      ? []
-      : (this._state?.providers || []).filter((entry) => entry.on === false);
-    if (dark.length)
-      this._setParams(
-        Object.fromEntries(dark.map((entry) => [entry.id, true])),
-      );
+    // The pill is the only switch: switching on also brings back Mapillary
+    // if a share link or a tool turned it off, or the layer would draw nothing.
+    if (!enabled && this._state?.providerOn === false)
+      this._setParams({ mapillary: true });
     try {
       await this.actions.setEnabled?.(!enabled);
     } catch (error) {