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>

docs/agent-log.md

@@ -4,6 +4,18 @@ What agents have done, newest first. Add an entry for every piece of work: the d
 note or request it was for, what changed, the files touched, the tests run, and anything left
 open or not verified. Keep each entry short; the git history has the details.
 
+## 2026-10-24: t21: piles near the bot sort quickly (Claude Code, Codex)
+
+- Owner: "a pile should sort when the player is nearby. the sorting shouldnt take long anyway."
+- `src/sim/cells.js`: `SORTP` 0.003 -> 0.06, `SORTP_FUEL` 0.003 for sinking through burning fuel
+  (at 0.06 dirt sank through a buried burning wood pile and `t_world`'s charcoal check failed);
+  `wakeBotPowder()` every 8 ticks from `simTick` wakes areas with loose grains (`powderArea`
+  hint, kept by `simMove`) within 100 grains of the bot. `worldSteps` settles at 0.003: seeds
+  unchanged.
+- Cost on a Medium dig site: 0.108 -> 0.134 ms/tick. `t_physics` sorting checks: near the bot ore
+  sorts in 432 ticks then sleeps; far away it stays; sand on dirt never sorts.
+- Tests: `run_all.py --browser` ALL PASSED.
+
 ## 2026-10-24: t21 phase 2: physics test pass for sand, molten metal and gases (Claude Code, Codex)
 
 - `test/t_physics.js` (41 checks): heaps, digging under a heap, ore sorting through ash, sand