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/content/kits_t5.test.js

@@ -3,7 +3,9 @@
 import { test } from 'node:test';
 import assert from 'node:assert/strict';
 import { makeBattle, enemyRec, chessRec, checkInvariants } from '../helpers/battleHarness.js';
-import KITS from '../../server/sim/content/kits/tier5.js';
+import { TIER_KITS } from '../../server/sim/content/kits/index.js';
+
+const KITS = TIER_KITS[4];
 
 const approx = (a, b, eps = 1e-6, msg = '') => assert.ok(Math.abs(a - b) <= eps * Math.max(1, Math.abs(b)), `${msg} ${a} ≉ ${b}`);
 const dummy = (key = 'enemy_dummy', o = {}) => enemyRec({ key, hp: 1e7, speed: 0, ...o });