feedback5 WE2: remove the kits/tier1-6.js re-export shims and shared/standIn.js diyRecord (#5)

Nothing but tests imported them: kits_t3 / kits_alt_t3 / kits_t4 / kits_t5 read
kits/index.js TIER_KITS, playtest5_elements / playtest6-combat / facing the real modules,
simServe checks /sim/content/kits/index.js; test/backups.test.js composes the prototypes
through shared/diy.js diyRecordOf at their locked selection. check:imports passes.
Docs: kits/README.md, DATA.md. Golden: no scenario moved.

test/sim/facing.test.js

@@ -12,7 +12,7 @@ import { COLS } from '../../server/sim/constants.js';
 import { makeBattle, chessRec, enemyRec, checkInvariants } from '../helpers/battleHarness.js';
 import { findSummonTile } from '../../server/sim/content/tokens.js';
 import { frontTile, sideTiles, alliesAround, N4 } from '../../server/sim/content/support/index.js';
-import { freeTileAround } from '../../server/sim/content/kits/tier1.js';
+import { freeTileAround } from '../../server/sim/content/kits/shared/tier1.js';
 import { DIRS as PROTOCOL_DIRS } from '../../shared/protocol.js';
 
 const K = (r, c) => r * COLS + c;