refactor(street-level): drop hover, legend and byte-budget cache; flatten the provider directory

- No pointer cursor over coverage lines (no other layer has one); a click
  test replaces the hover tests.
- No legend: one source, one colour.
- The on-globe credit lives in index.js; credits.js is gone.
- Billboard glyphs are SVG data URLs with the same geometry, so tests need
  no canvas stub.
- The tile cache keeps the 120 most recently used tiles, same 24 h TTL,
  instead of a byte budget; listTileLayers was test-only.
- providers/mapillary/ is flattened into the layer and its policy merged
  into one policy.js; the source's method list is a literal in the catalog.
- One fakeCesiumViewer for the layer tests.
- The fixture gate keeps the steps the unit tests do not cover: coverage and
  credit, a rejected key, line -> cone -> photo, close, a keyless page.

Co-Authored-By: Claude Fable 5.1 <[email protected]>

src/layers/streetLevel/decode.js

@@ -0,0 +1,40 @@
+import { PbfReader } from 'pbf';
+import { VectorTile } from '@mapbox/vector-tile';
+import { tileLocalToLonLat } from './tileMath.js';
+
+/**
+ * Decode a `mly1_public` coverage tile (z11–14) into sequences. The z14
+ * `image` layer, which can hold >150k points, is skipped.
+ * @param {Uint8Array} bytes
+ * @param {{x:number,y:number,z:number}} address
+ */
+export function decodeCoverageTile(bytes, address) {
+  const result = { sequences: [] };
+  if (!bytes || !bytes.length) return result;
+  const tile = new VectorTile(new PbfReader(bytes));
+  const { x, y, z } = address;
+  const sequenceLayer = tile.layers.sequence;
+  if (sequenceLayer) {
+    for (let i = 0; i < sequenceLayer.length; i++) {
+      const feature = sequenceLayer.feature(i);
+      const props = feature.properties || {};
+      // A sequence with a capture gap is a multi-line: keep each part as its
+      // own line, so no straight segment is drawn across the gap.
+      const parts = [];
+      for (const line of feature.loadGeometry()) {
+        const part = line.map((point) =>
+          tileLocalToLonLat(point.x, point.y, sequenceLayer.extent, x, y, z),
+        );
+        if (part.length >= 2) parts.push(part);
+      }
+      if (!parts.length) continue;
+      result.sequences.push({
+        id: String(props.id ?? feature.id ?? `${x}/${y}/${i}`),
+        capturedAt: Number(props.captured_at) || 0,
+        isPano: props.is_pano === true,
+        parts,
+      });
+    }
+  }
+  return result;
+}