Multi-core simulation: grain movement and heat across a worker pool (t88 phase 3)

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

test/fixtures/heat-chunk.js

@@ -1,4 +1,4 @@
-// Reference heat loop before t21 phase 3; preserves conduction and Float32 store order.
+// Unoptimized heat oracle, re-baselined for t88 chunk-pass heat outputs.
 function referenceHeatChunk(c, sc) {
   const cx = c % CW, cy = (c / CW) | 0;
   const x0 = cx << 5, y0 = cy << 5, x1 = Math.min(W, x0 + 32), y1 = Math.min(H, y0 + 32);
@@ -37,6 +37,8 @@ function referenceHeatChunk(c, sc) {
       if (flags[i] & F_BURN) burning = true;
     }
   }
-  if (burning || maxDev > 1.5) { hot[c] = 6; hotLvl[c] = (burning || maxDev > 60) ? 2 : 1; }
-  else hot[c]--;
+  const h = burning || maxDev > 1.5 ? 6 : hot[c] - 1;
+  const level = burning || maxDev > 1.5 ? ((burning || maxDev > 60) ? 2 : 1) : hotLvl[c];
+  if (chunkWork) { chunkWork.ownHot[c] = h; chunkWork.ownLevel[c] = level; }
+  else { hot[c] = h; hotLvl[c] = level; }
 }