Merge origin/main: Google Street View, KartaView and Panoramax on the slim Street Level

Main gained three imagery providers (Google Street View, KartaView,
Panoramax), shared line-coverage, cone and photo-viewer modules, one source
lit at a time and the translated interface. Their shared modules still
carried what this branch removes, so the merge ports them onto it:

- lineCoverage.js is this branch's coverage.js made provider-neutral
  (draped lines near the ground only, the selection drawn over them, key
  and rate-limit blocking); sequenceCones.js is sequences.js the same way.
  Mapillary, KartaView and Panoramax all build on them; Mapillary moves
  back to providers/mapillary/ beside the others.
- No ground casting, mesh sampling, surface modes, FOLLOW, legend, prewarm,
  orbit overview points (Panoramax's density dots included), stale-tile
  swaps or water-filled point budget come back.
- Kept from main because the new providers need them: requiresMapStack and
  attachMapStackController (Street View on Google 3D only), ground clicks,
  openNearest with an optional provider nearestImage, openImage {frame},
  reportError, the view-cone marker (now an SVG glyph), filters /
  coverageLabel / sinceBasis, OPEN STREET VIEW, keyAlternatives and i18n.
- photoViewer.js treats the viewer as expanded when its wrap is full screen
  or the iPhone popover, as EXPAND now is.
- The fixture browser gate keeps its 8 steps and adds one each for
  KartaView and Panoramax; catalogs, docs, boundaries and format scope
  follow.

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

src/services/meshFloorSampler.js

@@ -1,4 +1,5 @@
 import * as Cesium from 'cesium';
+import { approxDistanceKm } from '../data/approxDistance.js';
 
 /** Construct an instance-owned meshFloorSampler service with explicit dependencies. */
 export function createMeshFloorSampler({
@@ -79,16 +80,6 @@ export function createMeshFloorSampler({
     return false;
   }
 
-  /**
-   * Equirectangular distance (km) — same approximation the flights clamp uses.
-   */
-  function _approxKm(lat1, lon1, lat2, lon2) {
-    const dLat = (lat2 - lat1) * 111.32;
-    const dLon =
-      (lon2 - lon1) * 111.32 * Math.cos((((lat1 + lat2) / 2) * Math.PI) / 180);
-    return Math.hypot(dLat, dLon);
-  }
-
   /**
    * Samples the rendered mesh height for the coarse cells containing `points`,
    * one-shot per cell, budget-capped, viewer-proximity-gated. Call ONCE per
@@ -133,7 +124,8 @@ export function createMeshFloorSampler({
       if (
         Number.isFinite(viewerLat) &&
         Number.isFinite(viewerLon) &&
-        _approxKm(viewerLat, viewerLon, cell.lat, cell.lon) > MAX_SAMPLE_DIST_KM
+        approxDistanceKm(viewerLat, viewerLon, cell.lat, cell.lon) >
+          MAX_SAMPLE_DIST_KM
       ) {
         continue; // too far: tiles not streamed there, probe would be a guaranteed miss
       }