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/providers/mapillary/decode.test.mjs

@@ -17,7 +17,10 @@ function linePart(points) {
   return out;
 }
 
-/** A minimal mly1_public-shaped tile: one sequence line and one overview point. */
+/**
+ * A minimal mly1_public-shaped tile: one sequence line, plus one point in the
+ * low-zoom `overview` layer the layer never draws.
+ */
 function sampleTile({ geometry = null } = {}) {
   const writer = new PbfWriter();
   writer.writeMessage(
@@ -94,7 +97,7 @@ function sampleTile({ geometry = null } = {}) {
   return new Uint8Array(writer.finish());
 }
 
-test('sequences and overview points decode into lon/lat records', () => {
+test('sequences decode into lon/lat records; overview points are ignored', () => {
   const decoded = decodeCoverageTile(sampleTile(), { x: 0, y: 0, z: 1 });
   assert.equal(decoded.sequences.length, 1);
   const [sequence] = decoded.sequences;
@@ -109,19 +112,13 @@ test('sequences and overview points decode into lon/lat records', () => {
     'west half of tile 0/0 at z1',
   );
   assert.ok(lat0 > 0 && lat1 < lat0, 'northern hemisphere, moving south');
-  assert.equal(decoded.overview.length, 1);
-  assert.equal(decoded.overview[0].id, '3');
-  assert.equal(decoded.overview[0].isPano, false);
-  assert.ok(Math.abs(decoded.overview[0].lon - -90) < 1e-6, 'tile centre');
+  assert.deepEqual(Object.keys(decoded), ['sequences']);
 });
 
 test('an empty tile decodes to empty lists', () => {
   assert.deepEqual(
     decodeCoverageTile(new Uint8Array(0), { x: 0, y: 0, z: 0 }),
-    {
-      sequences: [],
-      overview: [],
-    },
+    { sequences: [] },
   );
 });