fix(street-level): deduplicate overlapping dateline tile halves

src/layers/streetLevel/street-level-unique-tiles.test.mjs

@@ -0,0 +1,15 @@
+import test from 'node:test';
+import assert from 'node:assert/strict';
+import { tilesForBbox } from './tileMath.js';
+test('coarse dateline coverage counts each tile exactly once', () => {
+  for (const z of [0, 1, 2]) {
+    const result = tilesForBbox([170, -1, -170, 1], z);
+    const keys = result.tiles.map((t) => `${t.x}/${t.y}/${t.z}`);
+    assert.equal(new Set(keys).size, keys.length);
+    assert.equal(result.total, keys.length);
+    const limited = tilesForBbox([170, -1, -170, 1], z, { limit: 1 });
+    assert.equal(limited.total, keys.length);
+    assert.equal(limited.truncated, keys.length > 1);
+    assert.equal(limited.tiles.length, 1);
+  }
+});

src/layers/streetLevel/tileMath.js

@@ -147,7 +147,12 @@ export function tilesForBbox(bbox, z, { limit = Infinity, focus = null } = {}) {
         return Math.min(dx, n - dx) ** 2 + (tile.y - centre.y) ** 2;
       };
   // Each tile's distance is computed once; ties keep their row order.
-  const ranked = tiles
+  const unique = [
+    ...new Map(
+      tiles.map((tile) => [`${tile.x}/${tile.y}/${tile.z}`, tile]),
+    ).values(),
+  ];
+  const ranked = unique
     .map((tile) => ({ tile, d: distance2(tile) }))
     .sort((a, b) => a.d - b.d)
     .map(({ tile }) => tile);