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/policy.js

@@ -1,11 +1,21 @@
-/** Identity and shared tuning for the Street Level layer. */
+/** Identity and tuning for the Street Level layer and its Mapillary imagery. */
 export const STREET_LEVEL_LAYER_ID = 'street-level';
+export const MAPILLARY_KEY_ID = 'mapillary';
+export const MAPILLARY_GRAPH_HOST = 'https://graph.mapillary.com';
 
 /** Pick id of the viewer position marker. */
 export const POSITION_PICK_ID = 'sl:pos';
 
-/** The selection highlight and the position marker. */
+/** Stable id prefixes for picked primitives; every one starts with `mly:`. */
+export const PICK_PREFIX = Object.freeze({
+  root: 'mly:',
+  sequence: 'mly:seq:',
+  image: 'mly:img:',
+});
+
+/** Mapillary green for lines and cones, GEV cyan for the selection, amber for the marker. */
 export const COLORS = Object.freeze({
+  coverage: '#05cb63',
   selected: '#00d4ff',
   position: '#ffb300',
 });
@@ -19,6 +29,44 @@ export const MAX_SINCE_DAYS = 36_500;
 /** Filter the layer starts with: all imagery, any date. */
 export const FILTER_DEFAULT = Object.freeze({ pano: 'all', sinceDays: 0 });
 
+/** Camera-driven coverage refresh. */
+export const COVERAGE_MOVE_DEBOUNCE_MS = 320;
+export const COVERAGE_MAX_TILES = 9;
+/** Shown when Mapillary refuses the server's token (401/403). */
+export const KEY_REJECTED_MESSAGE =
+  'Mapillary rejected MAPILLARY_CLIENT_TOKEN — replace it in Provider Settings';
+/** Shown while Mapillary rate-limits tile requests (429). */
+export const RATE_LIMITED_MESSAGE =
+  'Coverage requests are being rate-limited — they resume on their own';
+/**
+ * Street-zoom coverage reaches this far from the camera: camera height times
+ * the factor, never below the floor, even when a tilted view sees further.
+ */
+export const SEQUENCE_VIEW_RANGE_MIN_M = 2_500;
+export const SEQUENCE_VIEW_RANGE_PER_HEIGHT = 10;
+export const COVERAGE_MAX_SEQUENCES = 6000;
+export const COVERAGE_LINE_WIDTH_PX = 2.5;
+
+/** Per-sequence image cones after a sequence is selected. */
+export const SEQUENCE_IMAGES_LIMIT = 2000;
+export const IMAGE_CONE_SIZE_PX = 26;
+export const IMAGE_CONE_MIN_SPACING_M = 3;
+
+/** On-globe credit: Mapillary imagery is CC BY-SA 4.0 and needs attribution. */
+export const MAPILLARY_CREDIT_HTML =
+  'Street Level: imagery © <a href="https://www.mapillary.com" target="_blank" rel="noopener">Mapillary</a> contributors, CC BY-SA 4.0';
+
+/** Deep link to an image on mapillary.com, as the web app shares them. */
+export function mapillaryImageUrl(imageId) {
+  const id = String(imageId || '').trim();
+  if (!id) return 'https://www.mapillary.com/app/';
+  return `https://www.mapillary.com/app/?pKey=${encodeURIComponent(id)}&focus=photo`;
+}
+
+/** Fields requested for a sequence's images. */
+export const SEQUENCE_IMAGE_FIELDS =
+  'id,captured_at,compass_angle,geometry,is_pano';
+
 /** The key gate's label for the pill and the layer list, or null when the key is fine. */
 export function keyStatusLabel({ keyRequired, keyRejected }) {
   if (keyRejected) return 'KEY REJECTED';