WebGPU renderer complete: dirty uploads, default limits, legacy removed, WebGPU required, warm-up (t88 phase 2d)

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

src/sim/machines.js

@@ -57,7 +57,7 @@ function netSat(i) { if (POWER_FREE) return 1; const n = nets[netId[i]]; return
 // Move loose grains out of the given cells, to the nearest open cell above
 // the footprint in the same column (they then fall back on top). Gas just vanishes.
 function evictCells(cells, topY) {
-  for (const i of cells) bgm[i] = 0;
+  for (const i of cells) { bgm[i] = 0; renderDirtyIdx(i); }
   for (const i of cells) {
     const m = mat[i], ph = PH[m];
     if (m === EMPTY || ph === PH_SOLID) continue;