feedback5 WG: 补位 on the server — room.ownership { notOwned } (lenient check, stored per session / seat, a match takes the list its seat had at the start), PlayerState.standIns: the player's not-owned NORMAL chess fight as their stand-ins (battleInput standIn: true in every field, the stand-in's position / range, no summons), m.private.standIns, stand-in art in prep scouting

shared/standIn.js

@@ -101,6 +101,20 @@ export function composeUnitRecord(identity, unit, form, { skillIndex, moduleId =
   return out;
 }
 
+/**
+ * Whether a player may mark chess record `chess` as not owned (干员持有 → 下掉, the approved 0.2.0 补位 plan, owner's
+ * decision 2026-10-05): a NORMAL base chess (not the elite, not a 自选 slot) whose official stand-in is another
+ * character — the 55 chess of DATA.md §18 (53 of them in this season's shop; the hidden 百炼嘉维尔 t5 / 妮芙 t6 forms are
+ * retired). A PRESET (特许) chess always fields its own operator ("预设棋子…无论是否持有都由本人上场").
+ * @param {any} chess data/chess.json record
+ */
+export function isDroppableChess(chess) {
+  const b = chess && typeof chess === 'object' ? chess.backup : null;
+  return !!(b && !chess.isGolden && !chess.isDiy && chess.chessType === 'NORMAL'
+    && (!chess.baseId || chess.baseId === chess.chessId)
+    && typeof b.charId === 'string' && b.charId && b.charId !== chess.charId);
+}
+
 /**
  * The 补位 record of a chess: a NORMAL chess (normal or elite) fielded as its official stand-in — `backup.charId` at
  * the chess's own status, skill `backup.skillIndex`, module `backup.uniEquipId` (none when null), potential 0 — with