Piles near the bot sort, and 20 times faster; burning fuel keeps the slow pace (t21)

- SORTP 0.003 -> 0.06: ore sinks through 8 rows of ash in about 7 s near the bot.
- wakeBotPowder(): every 8 ticks, areas with loose grains within 100 grains of the bot get a
  sorting chance; far away, resting piles still sleep.
- Sinking through burning fuel stays at 0.003, so buried burning piles still char and furnace
  beds behave as tuned. World generation settles at the old rate: seeds are unchanged.

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

src/sim/worldgen.js

@@ -303,9 +303,9 @@ function* worldSteps(seedIn, w, h) {
   }
   fillNoise();
   yield [0.75, 'Settling loose ground'];
-  // settle loose material, with water at the speed it had when the seeds were made
+  // settle loose material at the water and sorting speeds the seeds were made with
   awake.fill(3);
-  const lstep = LSTEP, lfilm = LFILM; LSTEP = LFILM = 1;
+  const lstep = LSTEP, lfilm = LFILM, sortp = SORTP; LSTEP = LFILM = 1; SORTP = 0.003;
   for (let k = 0; k < 260; k++) {
     tick++; tickStamp = (tickStamp % 255) + 1;
     simMove();
@@ -313,7 +313,7 @@ function* worldSteps(seedIn, w, h) {
     if (!any) break;
     if ((k & 31) === 0) yield [0.75 + 0.24 * k / 260, 'Settling loose ground'];
   }
-  LSTEP = lstep; LFILM = lfilm;
+  LSTEP = lstep; LFILM = lfilm; SORTP = sortp;
   yield [0.99, 'Finishing'];
   // re-ambient after settling, then start clean
   for (let i = 0; i < N; i++) { const m = mat[i]; if (m !== MAGMA) temp[i] = AMB[(i / w) | 0]; life[i] = PH[m] === PH_LIQUID && FRZ[m] ? 255 : 0; }