chess.json: every record carries the shop row's backupCharId / backupTmplId / backupCharSkillIndex /
backupCharUniEquipId / backupCharPotRank verbatim as `backup` (both forms; nothing else changed).
data/backups.json: units = the 17 原型干员 with a form per status they fight at (43 forms: stats, trait,
talents, every unlocked skill, modules), diy = the 4 slots, the prototype picks per tier (9 6★ at 5 and 6,
six 4★ at 5), the 78 owned-6★ picks and their faction bonds (mainPower + subPower vs powerIdList, else 协防).
shared/standIn.js composes a stand-in (or a DIY prototype) into a chess-shaped record; the build fails when
the form builder cannot give back every PRESET chess field for field. test/backups.test.js (10 tests).