Pull nearest tilemap uvs a tenth of a texel in, 0.02 still showed lines

At 0.02 texel the lines between tiles of a nearest tilemap were gone at
the zooms tried first, but still showed at others. The user raised the
inset to 0.1 by hand and checked it in the browser.

- A tenth of a texel is still far below half a texel, so the texel
  picked at every pixel centre stays the same.
- The comment names the new value.

Tests:
- tilemap.test.ts follows the value: the inset test expects 0.1/96,
  the sliver test allows up to 0.25 texel from the edge, and the quad
  test checks its uvs to 2 digits instead of 3.
- ./check.sh: 156 files, 2314 tests, CHECK EXIT 0.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/viewport/tilemapMesh.ts

@@ -54,8 +54,8 @@ export function tileMesh(
   const half = tile / 2;
   // Linear sampling needs half a texel so the blend never reaches the neighbour. Nearest needs only
   // a sliver: at odd zooms a pixel centre on the quad edge can round onto the neighbour's first
-  // texel and draw a line. 1/50 texel keeps every picked texel the same.
-  const inset = sheet.smooth ? 0.5 : 0.02;
+  // texel and draw a line. 1/10 texel keeps every picked texel the same.
+  const inset = sheet.smooth ? 0.5 : 0.1;
   const insetX = inset / sheet.textureWidth;
   const insetY = inset / sheet.textureHeight;
   let v = 0;