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.test.mjs

@@ -1,127 +0,0 @@
-import assert from 'node:assert/strict';
-import test from 'node:test';
-import { createMapillarySource, MapillarySourceError } from './source.js';
-
-function fakeFetch(handler) {
-  const calls = [];
-  const fetchImpl = async (url, init = {}) => {
-    calls.push({ url: String(url), init });
-    return handler(String(url), init);
-  };
-  return { calls, fetchImpl };
-}
-
-const jsonResponse = (payload, status = 200) =>
-  new Response(JSON.stringify(payload), {
-    status,
-    headers: { 'content-type': 'application/json' },
-  });
-
-test('tiles go through the local proxy and never carry the token', async () => {
-  const { calls, fetchImpl } = fakeFetch(
-    () => new Response(new Uint8Array([1, 2, 3]), { status: 200 }),
-  );
-  const source = createMapillarySource({ token: 'MLY|1|abc', fetchImpl });
-  const bytes = await source.getTile('coverage', 14, 2662, 6285);
-  assert.deepEqual([...bytes], [1, 2, 3]);
-  assert.equal(calls[0].url, '/api/mapillary/tiles/coverage/14/2662/6285');
-  assert.doesNotMatch(calls[0].url, /MLY/);
-});
-
-test('an empty tile (204) is an empty byte array, not an error', async () => {
-  const { fetchImpl } = fakeFetch(() => new Response(null, { status: 204 }));
-  const source = createMapillarySource({ token: 'MLY|1|abc', fetchImpl });
-  assert.equal((await source.getTile('coverage', 14, 1, 1)).length, 0);
-});
-
-test('a missing key on the proxy surfaces as keyRequired', async () => {
-  const { fetchImpl } = fakeFetch(() =>
-    jsonResponse({ error: 'no_key', keyRequired: true }, 503),
-  );
-  const source = createMapillarySource({ token: '', fetchImpl });
-  assert.equal(source.hasToken(), false);
-  await assert.rejects(
-    () => source.getTile('coverage', 14, 1, 1),
-    (error) =>
-      error instanceof MapillarySourceError &&
-      error.status === 503 &&
-      error.keyRequired === true,
-  );
-});
-
-test('graph lookups call graph.mapillary.com with the client token and requested fields', async () => {
-  const { calls, fetchImpl } = fakeFetch(() =>
-    jsonResponse({ data: [{ id: '1', geometry: { coordinates: [1, 2] } }] }),
-  );
-  const source = createMapillarySource({ token: 'MLY|1|abc', fetchImpl });
-  const images = await source.getSequenceImages('seq-1');
-  assert.equal(images.length, 1);
-  const url = new URL(calls[0].url);
-  assert.equal(url.host, 'graph.mapillary.com');
-  assert.equal(url.pathname, '/images');
-  assert.equal(url.searchParams.get('access_token'), 'MLY|1|abc');
-  assert.equal(url.searchParams.get('sequence_ids'), 'seq-1');
-  assert.match(url.searchParams.get('fields'), /geometry/);
-});
-
-test('graph calls without a token fail fast as keyRequired without a request', async () => {
-  const { calls, fetchImpl } = fakeFetch(() => jsonResponse({}));
-  const source = createMapillarySource({ token: '', fetchImpl });
-  await assert.rejects(
-    () => source.getSequenceImages('123'),
-    (error) =>
-      error instanceof MapillarySourceError && error.keyRequired === true,
-  );
-  assert.equal(calls.length, 0);
-});
-
-test('graph API errors carry the upstream message and status', async () => {
-  const { fetchImpl } = fakeFetch(() =>
-    jsonResponse({ error: { message: 'Invalid OAuth 2.0 Access Token' } }, 400),
-  );
-  const source = createMapillarySource({ token: 'MLY|1|abc', fetchImpl });
-  await assert.rejects(
-    () => source.getSequenceImages('999'),
-    (error) =>
-      error instanceof MapillarySourceError &&
-      error.status === 400 &&
-      /Invalid OAuth/.test(error.message),
-  );
-});
-
-test('a rejected key and a rate limit are told apart from other tile errors', async () => {
-  const rejectedSource = createMapillarySource({
-    token: 'MLY|1|abc',
-    fetchImpl: fakeFetch(() =>
-      jsonResponse(
-        { error: 'Mapillary rejected the access token', keyRejected: true },
-        403,
-      ),
-    ).fetchImpl,
-  });
-  await assert.rejects(
-    () => rejectedSource.getTile('coverage', 14, 1, 1),
-    (error) =>
-      error.keyRejected === true &&
-      error.keyRequired === false &&
-      error.retryAfterSec === null,
-  );
-  const limitedSource = createMapillarySource({
-    token: 'MLY|1|abc',
-    fetchImpl: fakeFetch(
-      () =>
-        new Response(
-          JSON.stringify({ error: 'rate limited', retryAfter: 45 }),
-          {
-            status: 429,
-            headers: { 'retry-after': '30' },
-          },
-        ),
-    ).fetchImpl,
-  });
-  await assert.rejects(
-    () => limitedSource.getTile('coverage', 14, 1, 1),
-    (error) => error.retryAfterSec === 30 && error.keyRejected === false,
-    'the Retry-After header wins over the body',
-  );
-});