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/selection.test.mjs

@@ -58,17 +58,23 @@ function harness({ selected = false } = {}) {
   const state = {
     viewer,
     enabled: true,
+    providerOn: true,
     clickHandler: null,
     services: { picking: null, input: null },
+    sequence: {
+      get selectedId() {
+        return sequences.selected ? 'seq-1' : null;
+      },
+    },
   };
   const selection = createSelection({
     state,
     parts: {
-      router: { ownsPick: (id) => id === 'mly:seq:1', resolve: () => null },
-      hasSelectedSequence: () => sequences.selected,
-      clearSequences() {
-        sequences.cleared++;
-        sequences.selected = false;
+      sequences: {
+        clearSelection() {
+          sequences.cleared++;
+          sequences.selected = false;
+        },
       },
     },
   });