fix(street-level): budgeted mesh sampling, in-place cones, date line, horizon

From the IC8 review of #768, each with tests that fail before:

- P1: a mesh batch no longer rebuilds the selected sequence's cones. The
  drawn cones are indexed by mesh cell; a batch that touches none of them
  is ignored and the affected cones are moved in place (no removeAll/add).
- P2: mesh sampling keeps to its 6 ms slices. Requests are taken in inside
  the budget, only cells within range of the camera are queued, the queue
  is a persistent min-heap re-ranked in one pass only after a 100 m camera
  move, and the deadline starts before any work. Coverage keeps a bounding
  box per line and densifies a line only once it comes within range. On a
  synthetic dense tile (600 x 40 points): slice median ~10 ms -> 5 ms, max
  18-30 ms -> 6.7 ms, refresh cost 11-24 ms -> 1.5-3 ms.
- P2: image cones and the photo marker are horizon-culled like the
  overview dots (one createHorizonCull in view.js, shared by all three).
- P2: a selection change recolours the previous zoom's lines still on
  screen and the old lines a cast swap keeps showing.
- P2: distances (metresBetween), line densification and ground-corner
  requests go the short way round +-180 deg (wrapLon in tileMath.js), so
  nearest ordering, cone thinning, mesh range and cast lines are right
  across the date line.

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

src/layers/streetLevel/tileMath.js

@@ -9,6 +9,15 @@ function clampLat(lat) {
   return Math.max(-MAX_LAT, Math.min(MAX_LAT, lat));
 }
 
+/**
+ * A longitude, or the difference of two, wrapped into [-180, 180]: the short
+ * way round the date line. Values already in range come back unchanged.
+ */
+export function wrapLon(lon) {
+  if (lon >= -180 && lon <= 180) return lon;
+  return ((((lon + 180) % 360) + 360) % 360) - 180;
+}
+
 /** Fractional tile column of a longitude in [-180, 180] at zoom z. */
 function tileXAt(lon, z) {
   return ((lon + 180) / 360) * 2 ** z;
@@ -27,8 +36,7 @@ export function lonToTileX(lon, z) {
   const n = 2 ** z;
   // 180° is the east edge of the last column, not the west edge of the first.
   if (lon >= 180) return n - 1;
-  const wrapped = ((((lon + 180) % 360) + 360) % 360) - 180;
-  return Math.min(n - 1, Math.max(0, Math.floor(tileXAt(wrapped, z))));
+  return Math.min(n - 1, Math.max(0, Math.floor(tileXAt(wrapLon(lon), z))));
 }
 
 /** Tile row for a latitude at zoom z. */