refactor(street-level): one provider, no orbit overview, no prewarm, simpler tile choice

The layer now owns its Mapillary parts directly: the provider registry,
pick router, multi-provider UI summary, params codec helper and provider
context are gone. createStreetLevelLayer({ source }) builds coverage,
sequences, the nearest-image lookup and the MapillaryJS viewer itself; a
single providerOn switch keeps the share link's `mapillary` option (off
draws nothing), and getParams/setParams keep { mapillary, pano, sinceDays }.

No z0-5 overview points: above 60 km nothing is drawn and the panel says to
zoom in; the proxy now serves only coverage z11-14. Tiles come from the
visible ground within range of the camera, ranked from the ground under it
(no line-of-sight ranking or near-range padding). MapillaryJS loads on the
first photo; viewer prewarm is removed. Key status, a rejected key and a
rate limit share one `blocked` state on coverage.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

src/layers/streetLevel/uiState.js

@@ -1,74 +0,0 @@
-import { COLORS } from './policy.js';
-
-/**
- * @typedef {object} ProviderSnapshot
- * @property {string} id
- * @property {string} name
- * @property {string} label
- * @property {boolean} on
- * @property {boolean|null} configured   null until the status call answers
- * @property {boolean} keyRequired   no usable key: missing or rejected
- * @property {boolean} [keyRejected] the provider refused the configured key
- * @property {string|null} requiresKeyId
- * @property {boolean} loading
- * @property {number} count
- * @property {string} hint
- * @property {string|null} error
- * @property {string} color   The source's one colour.
- */
-
-/**
- * Totals over switched-on providers. Key-gated only when every one lacks its
- * key; `keyRejected` when that is because a key was refused.
- * @param {Array<ProviderSnapshot>} providers
- */
-export function summarizeCoverage(providers) {
-  const active = providers.filter((p) => p.on);
-  return {
-    count: active.reduce((sum, p) => sum + (p.count || 0), 0),
-    loading: active.some((p) => p.loading),
-    hint: active.find((p) => p.hint)?.hint || '',
-    error: active.find((p) => p.error)?.error || null,
-    keyRequired:
-      active.length > 0 && active.every((p) => p.keyRequired === true),
-    keyRejected:
-      active.length > 0 &&
-      active.every((p) => p.keyRequired === true) &&
-      active.some((p) => p.keyRejected === true),
-  };
-}
-
-/**
- * The panel snapshot from core state and provider snapshots. The legend has
- * one swatch per active source, then the shared selection colour.
- * @param {{enabled: boolean, filter: object, providers: Array<ProviderSnapshot>, street: object, sequence: object}} input
- */
-export function composeUIState({
-  enabled,
-  filter,
-  providers,
-  street,
-  sequence,
-}) {
-  const active = providers.filter((p) => p.on);
-  const { keyRequired, keyRejected, ...coverage } =
-    summarizeCoverage(providers);
-  const legend = active.map((provider) => ({
-    key: provider.id,
-    label: provider.name,
-    color: provider.color,
-  }));
-  if (active.length)
-    legend.push({ key: 'selected', label: 'Selected', color: COLORS.selected });
-  return {
-    enabled,
-    keyRequired,
-    keyRejected,
-    filter: { ...filter },
-    providers: providers.map((p) => ({ ...p })),
-    coverage,
-    legend,
-    sequence: { ...sequence },
-    street: { ...street },
-  };
-}