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/tooling/streetLevelQa.test.mjs

@@ -1,89 +1,14 @@
 import assert from 'node:assert/strict';
 import test from 'node:test';
-import { fixtureTile } from '../../scripts/qa-street-level.mjs';
 import {
   answerMapillaryRequest,
   describeCall,
-  PHOTO_LINE,
   PHOTO_SEQUENCE_ID,
   photoImages,
   THUMB_HOST,
 } from '../../scripts/fixtures/street-level/mapillaryGraph.mjs';
 import { redact } from '../../scripts/qa-browserEvidence.mjs';
 
-test('fixture tiles give the hermetic gate something real to filter', async () => {
-  const { decodeCoverageTile } =
-    await import('../layers/streetLevel/providers/mapillary/decode.js');
-  const now = Date.UTC(2026, 9, 1);
-  const street = decodeCoverageTile(fixtureTile(14, 2662, 6286, now), {
-    x: 2662,
-    y: 6286,
-    z: 14,
-  });
-  const grid = street.sequences.filter((s) => s.id !== PHOTO_SEQUENCE_ID);
-  assert.equal(grid.length, 8);
-  const pano = grid.filter((s) => s.isPano).length;
-  assert.ok(pano > 0 && pano < 8, '360° and flat both present');
-  const year = 365 * 86_400_000;
-  const old = grid.filter((s) => now - s.capturedAt > year).length;
-  assert.ok(old > 0 && old < 8, 'recent and older both present');
-  assert.equal(fixtureTile(3, 1, 3, now).length, 0, 'nothing from orbit');
-  assert.equal(fixtureTile(8, 1, 1, now).length, 0, 'nor in between');
-});
-
-/* ── Hermetic photo flow: the photo line and the Graph fixtures ────────── */
-
-test('the photo sequence runs through the parked view, clipped to each tile it crosses', async () => {
-  const { decodeCoverageTile } =
-    await import('../layers/streetLevel/providers/mapillary/decode.js');
-  const { lonToTileX, latToTileY } =
-    await import('../layers/streetLevel/tileMath.js');
-  const x = lonToTileX(PHOTO_LINE.lon, 14);
-  const rows = new Set(
-    [PHOTO_LINE.south, PHOTO_LINE.north].map((lat) => latToTileY(lat, 14)),
-  );
-  assert.ok(rows.size > 1, 'the line crosses a tile edge');
-  let south = Infinity;
-  let north = -Infinity;
-  for (const y of rows) {
-    const line = decodeCoverageTile(fixtureTile(14, x, y), {
-      x,
-      y,
-      z: 14,
-    }).sequences.find((s) => s.id === PHOTO_SEQUENCE_ID);
-    assert.ok(line, `tile 14/${x}/${y} carries the photo line`);
-    for (const [lon, lat] of line.parts[0]) {
-      assert.ok(Math.abs(lon - PHOTO_LINE.lon) < 1e-4);
-      south = Math.min(south, lat);
-      north = Math.max(north, lat);
-    }
-  }
-  assert.ok(Math.abs(south - PHOTO_LINE.south) < 1e-4);
-  assert.ok(Math.abs(north - PHOTO_LINE.north) < 1e-4);
-  // Far away there is no photo line, only the grid.
-  const elsewhere = decodeCoverageTile(fixtureTile(14, 100, 100), {
-    x: 100,
-    y: 100,
-    z: 14,
-  });
-  assert.equal(
-    elsewhere.sequences.some((s) => s.id === PHOTO_SEQUENCE_ID),
-    false,
-  );
-});
-
-test('the fixture photos: one sequence, 360° and flat, spaced past the cone thinning', () => {
-  const images = photoImages(Date.UTC(2026, 9, 1));
-  assert.ok(images.length >= 3);
-  assert.ok(images.some((image) => image.isPano));
-  assert.ok(images.some((image) => !image.isPano));
-  for (let i = 1; i < images.length; i++) {
-    const gap = (images[i].lat - images[i - 1].lat) * 110_540;
-    assert.ok(gap > 3, `gap ${gap}`);
-  }
-  assert.equal(new Set(images.map((image) => image.id)).size, images.length);
-});
-
 const graph = (path, params) =>
   `https://graph.mapillary.com/${path}?${new URLSearchParams({ access_token: 'MLY|0|qa-fixture', ...params })}`;
 const answer = (url, method = 'GET') => {
@@ -94,22 +19,6 @@ const answer = (url, method = 'GET') => {
   };
 };
 
-test('the Graph fixtures answer the provider’s sequence lookups', () => {
-  const images = photoImages();
-  const sequence = answer(
-    graph('images', {
-      sequence_ids: PHOTO_SEQUENCE_ID,
-      fields: 'id,geometry,compass_angle,captured_at,is_pano',
-      limit: '2000',
-    }),
-  );
-  assert.equal(sequence.json.data.length, images.length);
-  assert.deepEqual(
-    answer(graph('images', { sequence_ids: 'other', fields: 'id' })).json.data,
-    [],
-  );
-});
-
 test('the Graph fixtures answer every call MapillaryJS makes to open a photo', () => {
   const [first, second] = photoImages();
   const spatial = answer(