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/providers/mapillary/source.js

@@ -1,127 +0,0 @@
-import {
-  MAPILLARY_GRAPH_HOST,
-  SEQUENCE_IMAGE_FIELDS,
-  SEQUENCE_IMAGES_LIMIT,
-} from './policy.js';
-
-/** HTTP error flagged `keyRequired`, `keyRejected` or `retryAfterSec` (429). */
-export class MapillarySourceError extends Error {
-  constructor(message, { status = 0, payload = null, retryAfterSec } = {}) {
-    super(message);
-    this.name = 'MapillarySourceError';
-    this.status = status;
-    this.payload = payload;
-    this.keyRequired = payload?.keyRequired ?? payload?.error === 'no_key';
-    this.keyRejected = payload?.keyRejected === true;
-    const wait = Number(retryAfterSec ?? payload?.retryAfter);
-    this.retryAfterSec =
-      status === 429 ? (Number.isFinite(wait) && wait > 0 ? wait : 60) : null;
-  }
-}
-
-async function readJsonOrThrow(response, label) {
-  let payload = null;
-  try {
-    payload = await response.json();
-  } catch {
-    /* status is authoritative */
-  }
-  if (!response.ok)
-    throw new MapillarySourceError(
-      payload?.error?.message ||
-        payload?.error ||
-        `${label} HTTP ${response.status}`,
-      { status: response.status, payload },
-    );
-  return payload;
-}
-
-/**
- * Mapillary network access: tiles via the local proxy, which adds the token
- * and caches; Graph API lookups direct with the client token, as MapillaryJS.
- * @param {{token?: string, fetchImpl?: Function, endpoints?: object}} options
- */
-export function createMapillarySource({
-  token = '',
-  fetchImpl = (...args) => globalThis.fetch(...args),
-  endpoints = {},
-} = {}) {
-  const urls = {
-    status: '/api/mapillary/status',
-    tiles: '/api/mapillary/tiles',
-    graph: MAPILLARY_GRAPH_HOST,
-    ...endpoints,
-  };
-
-  async function graph(path, params = {}, { signal } = {}) {
-    if (!token)
-      throw new MapillarySourceError('Mapillary token not configured', {
-        status: 503,
-        payload: { keyRequired: true },
-      });
-    const search = new URLSearchParams({ access_token: token, ...params });
-    const response = await fetchImpl(`${urls.graph}/${path}?${search}`, {
-      signal,
-    });
-    return readJsonOrThrow(response, 'Mapillary graph');
-  }
-
-  return {
-    get token() {
-      return token;
-    },
-    hasToken: () => Boolean(token),
-
-    async getStatus({ signal } = {}) {
-      const response = await fetchImpl(urls.status, {
-        signal,
-        cache: 'no-store',
-      });
-      return readJsonOrThrow(response, 'Mapillary status');
-    },
-
-    /** Raw protobuf bytes for one tile; an empty array means no data. */
-    async getTile(layer, z, x, y, { signal } = {}) {
-      const response = await fetchImpl(
-        `${urls.tiles}/${layer}/${z}/${x}/${y}`,
-        {
-          signal,
-        },
-      );
-      if (response.status === 204) return new Uint8Array(0);
-      if (!response.ok) {
-        let payload = null;
-        try {
-          payload = await response.json();
-        } catch {
-          /* ignore */
-        }
-        throw new MapillarySourceError(
-          payload?.error || `Tile HTTP ${response.status}`,
-          {
-            status: response.status,
-            payload,
-            retryAfterSec: response.headers?.get?.('retry-after') ?? undefined,
-          },
-        );
-      }
-      return new Uint8Array(await response.arrayBuffer());
-    },
-
-    async getSequenceImages(
-      sequenceId,
-      { signal, limit = SEQUENCE_IMAGES_LIMIT } = {},
-    ) {
-      const payload = await graph(
-        'images',
-        {
-          sequence_ids: String(sequenceId),
-          fields: SEQUENCE_IMAGE_FIELDS,
-          limit: String(limit),
-        },
-        { signal },
-      );
-      return Array.isArray(payload?.data) ? payload.data : [];
-    },
-  };
-}