feedback1 cell: bots let their placement step judge the operator a 突变细胞 transformation gained

With the bench rule the gained operator starts the next prep on the bench while its carrier's deployment
is free. The buy loop's pre-emptive bench shed sells the weakest bench single by piece value while the
bench is crowded, before the placement step runs: in 20 solo 绝境 matches on 昆图斯 it sold 44 of 222
gained operators that way.

- bot.js: botPrepEndSteps remembers the chess owned when the prep ends (rememberOwned); the shed's
  keepFresh now also spares a piece gained since then (a transformation's operator, battle-result /
  round-start grants), so the lineup step decides about it. No memory yet (a first prep, a seat just
  put under AI 托管) changes nothing.
- botbench, decisions only: 昆图斯 (seeds 201-220) 绝境 7 -> 11 / 20 wins with the fix (8 on the WA
  build), 险境 16 -> 17 / 20 (15); the bots' own strategies unchanged within noise (solo 绝境 8 / 12 both,
  solo 险境 19 / 24 both, co-op 绝境 4 AI 9 -> 8 / 36).
- Test: a real solo 绝境 昆图斯 bot match (seed 9 sold its R7 operator in the R8 prep before the fix):
  no gained operator shed in its first prep, none waiting on the bench beside a free deployment.
- DESIGN §21.1 / §21.6 / §6.6, META and the CHANGELOG line say so.

docs/META.md

@@ -238,7 +238,9 @@ gets a hand slot made for it, `makeHandRoom` — on a bot's own seat by destroyi
 chess can be sold, never a human's item under AI 托管 — on such a seat any item left in temp with a full hand gets a
 hand slot the same way, a bench operator sold for it; only a hand of nothing but items still drops it, as the temp
 deadline would; the operator a transformation gains waits on the bench and the next prep's lineup step deploys it
-like any owned unit — AI 托管 too), 身份牌 / 通讯机 / 寻呼模块 on a focus member; 画卷 copies the most
+like any owned unit — AI 托管 too; the buy loop's bench shed, which sells by piece value while the bench is crowded,
+never sells a piece gained since the bot's last prep ended, `rememberOwned`), 身份牌 / 通讯机 / 寻呼模块 on a focus
+member; 画卷 copies the most
 valuable deployed operator; 教鞭 / “神秘顾客” are used after a perfect battle and otherwise kept in the hand — a bot drops
 a kept one only when it needs the hand slot (“神秘顾客” then pays its fund), a human's seat under AI 托管 never. 机变: a
 bounty card is scored by its expected payout minus its expected leaks × the value of an LP (2 + 20 / LP), the kill