The ground gets cast: per-pixel floor and ceiling, both paintable

True floor-casting replaces the gradients and the projected seam lines:
every screen row lies at one depth, walked with a constant world-space
step and sampled from floor.png underfoot and ceiling.png overhead —
each maze cell wearing exactly one tile, so the artist's border IS the
cell seam. Distance shade and fog fold into the same per-pixel pass,
pixel buffers cache per texture (re-read when a painted file lands),
and the whole frame still clears 60fps with room to spare. Flagstones
and dark slabs ship as the starter files beside the other masonry.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

packages/web/src/TokenGallery.svelte

@@ -94,7 +94,7 @@
     wherever a file is missing.
   </p>
   <div class="grid">
-    {#each ["wall", "rim", "stone", "door", "firewall", "warp"] as name (name)}
+    {#each ["wall", "rim", "stone", "door", "firewall", "warp", "floor", "ceiling"] as name (name)}
       <figure>
         <img class="masonry" src={`/textures/${name}.png`} alt={`${name} texture`} />
         <figcaption>{name}</figcaption>