feedback1 cell: a 突变细胞 transformation gains the new operator into the 整备区 and frees the carrier's tile (pointed out in PR #2)

Official gameplay footage (bilibili BV1vzyVBuEN9 at about 8:24, BV1Qkw1zMEoR at about 7:25) shows the
next prep with the carrier's tile empty, one more deployment left, and the returned equipment plus the
new tier+1 operator on the bench, deployed by hand afterwards. That is the PRTS 备注 read as written
("生效时，原干员销毁，获得一名高一阶的随机初始干员"): a destroy followed by a gain. The closed PR #2 made
the same claim from a playtest.

- PlayerState.transformChess: the carrier is destroyed wherever it stands (board tile freed, summons
  removed, copies back to the pool); its equipment, the cell included, returns to the hand first
  (overflow temp, auto-merge); then the new operator is gained through acquireChess like any gained
  operator (hand, overflow temp, the no-room rule of every gain; no summon card until it is deployed).
  The returnItems option is gone (the cell's built-in was its only caller).
- A merge the gain completes merges like any gained copy: the elite takes a consumed deployed copy's
  tile, else the hand. _mergeChess loses fromKey / fromDir, so the destroyed carrier's tile never
  counts (PR #2 had kept that path; not adopted); audit.js drops its exception for it.
- builtinMeta, ctx.transform, items/meta.js and bot.js comments follow. Bots and AI 托管 deploy the
  gained operator in their normal lineup step (no bot change needed; a real co-op round pins it).
- ITEM_RULES note and implFormula for the item card; data/items.json rebuilt with build-data --offline.
- Tests: facing, merge, playtest6-elite-to-board and items no longer pin the kept tile; feedback1-meta
  covers a deployed and a bench carrier, hand full -> temp, hand and temp full, a merge with and
  without a deployed copy (never the carrier's tile), 商业包装方案's count on the returned item, and bots /
  AI 托管 redeploying; feedback1-cell checks the new note.

server/match/bot.js

@@ -53,7 +53,8 @@
 //   5. items by what they do (itemTarget): equipment on the strongest deployed damage dealers (survival items on
 //      blockers, bond signature items on a member), 信标 on a bench single, 拟态物质 on a pair, 博士投影 (both
 //      qualities) on the strongest normal operator, 突变细胞 on the least valuable normal single below 6阶 (cellTarget:
-//      never an elite or a pair member), bond items on a focus member; Arts (useArt): 画卷 copies the most valuable
+//      never an elite or a pair member; the operator its transformation gains joins the bench and steps 3–4 of the next
+//      prep deploy it like any owned unit), bond items on a focus member; Arts (useArt): 画卷 copies the most valuable
 //      deployed operator, 教鞭 / “神秘顾客” are used after a perfect battle and kept otherwise (consume-on-equip items /
 //      Arts only with a handler)
 //   6. resolve the temp slots (a 突变细胞 left there — it comes back after every transformation — gets a hand slot made
@@ -1613,7 +1614,8 @@ const isMutationCell = (gd, itemId) => itemEffect(gd.item(itemId)) === 'char_che
 
 /**
  * Whom the bot injects with 突变细胞 (after the battle its carrier — deployed or on the bench: every owned carrier's item
- * hooks run — becomes a random operator one tier higher; items meta char_chess_transformation_equip): the least
+ * hooks run — is destroyed and a random operator one tier higher joins the bench, PlayerState.transformChess; the next
+ * prep's lineup step deploys it like any owned unit, so a deployed carrier only costs a re-placement): the least
  * valuable normal operator below 6阶 with a free equip slot — never an elite, never one of a merge pair (the merge
  * progress would be lost), nobody already carrying a cell. null: the cell waits in the hand.
  */