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/view.test.mjs

@@ -3,6 +3,7 @@ import test from 'node:test';
 import * as Cesium from 'cesium';
 import {
   cameraHeightAboveGround,
+  metresBetween,
   viewCentre,
   viewFocus,
   visibleBbox,
@@ -146,3 +147,23 @@ test('looking at the horizon from eye height still boxes the ground around the c
   assert.ok(north - 38.5816 > 0.008 && 38.5816 - south > 0.008);
   assert.ok(east - -121.4944 > 0.008 && -121.4944 - west > 0.008);
 });
+
+test('metresBetween measures the short way round the date line (review IC8 P2)', () => {
+  const east = { lon: 179.9999, lat: 0 };
+  const west = { lon: -179.9999, lat: 0 };
+  // 0.0002° of longitude at the equator, not 40,000 km round the other way.
+  assert.ok(Math.abs(metresBetween(east, west) - 22.264) < 1e-6);
+  assert.ok(Math.abs(metresBetween(west, east) - 22.264) < 1e-6);
+  assert.ok(
+    Math.abs(
+      metresBetween({ lon: 180, lat: 0 }, { lon: -180, lat: 0.0001 }) - 11.054,
+    ) < 1e-6,
+    'the two names of the same meridian',
+  );
+  // Away from the date line nothing changes.
+  assert.ok(
+    Math.abs(
+      metresBetween({ lon: 10, lat: 0 }, { lon: 10.001, lat: 0 }) - 111.32,
+    ) < 1e-9,
+  );
+});