feedback5 WD: the sim fields a 补位 stand-in — getChess(id, { standIn: true }) over data/backups.json, PlayerBattleInput standIn: true, kits by the stand-in's charId (never the replaced operator's), kits/ops/standin-<codename>.js registry, harness standIn

- simdata: DataSource keeps `backups` (rawBackups follows the fallback chain); getStandIn = shared/standIn.js
  standInRecord normalised (the chess's ids / bonds / 特质 / tier, the stand-in's body, def.standInFor); a PRESET / DIY
  chess or a source without backups fields itself; the per-battle view maps id-only lookups.
- spec.js keeps `standIn` only when exactly true (never on a token); Battle passes it to getChess; syncUnitLoadout
  carries it; UnitInfo `standInFor`.
- content/index.js kitOf: a stand-in's kit is KITS[def.charId] only; no default skill (a stand-in kit writes `skills`);
  without a kit the generic kit plus genericTalents. kits/index.js STANDIN_KIT_FILES / STANDIN_KITS, merged after the
  tier groups (old keys keep their order; golden unchanged).
- server/data.js and tools/setup.mjs expect backups.json.
- test/content/standin.test.js: the plumbing and the eight 预备干员 on all 28 chess records they replace.

tools/setup.mjs

@@ -44,7 +44,7 @@ const NODE_URL = 'https://nodejs.org/zh-cn/download';
 
 /** Data files the server expects (server/data.js DATA_FILES) + the emote catalogue used by the client. */
 export const DATA_FILES = ['config', 'chess', 'bonds', 'garrisons', 'items', 'bands', 'effects', 'choices',
-  'enemies', 'factions', 'waves', 'stages', 'bosses', 'tokens', 'assets', 'emotes'];
+  'enemies', 'factions', 'waves', 'stages', 'bosses', 'tokens', 'assets', 'backups', 'emotes'];
 /** Runtime packages that must be installed (package.json dependencies). */
 export const RUNTIME_PACKAGES = ['ws', 'pixi.js', 'pixi-spine', 'preact', 'htm'];
 /** Vendor files the client cannot run without (tools/vendor.mjs; three.js is optional there). */