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/layers/streetLevel/policy.js

@@ -1,15 +1,10 @@
-/** Identity and shared tuning for the provider-neutral Street Level layer. */
+/** Identity and shared tuning for the Street Level layer. */
 export const STREET_LEVEL_LAYER_ID = 'street-level';
 
-/** Pick id of the viewer position marker; the core owns it, not a provider. */
+/** Pick id of the viewer position marker. */
 export const POSITION_PICK_ID = 'sl:pos';
 
-/** One colour per imagery source: chip, coverage lines, points, cones and legend. */
-export const PROVIDER_COLORS = Object.freeze({
-  mapillary: '#05cb63',
-});
-
-/** Colours every provider shares: the selection highlight and the marker. */
+/** The selection highlight and the position marker. */
 export const COLORS = Object.freeze({
   selected: '#00d4ff',
   position: '#ffb300',
@@ -21,8 +16,5 @@ export const PANO_MODES = Object.freeze(['all', 'pano', 'flat']);
 /** Longest "captured since" window the filter accepts, in days (~100 years). */
 export const MAX_SINCE_DAYS = 36_500;
 
-/** Filter every provider starts with: all imagery, any date. */
+/** Filter the layer starts with: all imagery, any date. */
 export const FILTER_DEFAULT = Object.freeze({ pano: 'all', sinceDays: 0 });
-
-/** Nearest-image search radius in metres (Mapillary's graph API caps it at 50 m). */
-export const NEAREST_RADIUS_M = 50;