feedback7: the battle sim uses engine-independent math — Chrome, Firefox, Safari and the server agree bit for bit (PR #373 by @Cloudnyco)

- server/sim/detmath.js: hypot (sqrt of the squares, rescaled outside 2^±500), powi (integer powers in double-double,
  one rounding), sin / cos (fdlibm 5.3) and atan2 (fdlibm / FreeBSD msun) built only from correctly rounded IEEE
  operations; the sim's Math.hypot / sin / cos / atan2 / pow calls go through it (65 files); eslint.config.js forbids
  the approximated Math functions under server/sim and test/sim/detmath.test.js scans for them.
- sin / cos / atan2 are the algorithms V8 runs in Node, so the server's results stay; only hypot differs from V8's.
  Golden: 2 moved — diy-027 (a hypot distance, damage +80) and coop3-ABYSS-5 (a later card pick from round 9, same end).
- Applied unchanged after review (Grok static review: MERGE; the diff read in full: no network, no new dependency).
- Tests: broad node --test 5155 / 5155 with the new file tracked (detmath 7 / 7, package 10 / 10); lint 0 errors,
  typecheck, check:imports.

server/sim/content/kits/ops/op-ebnhlz.js

@@ -67,6 +67,7 @@ import { num, talentBb, moduleBb, traitBb, skillRec, batMod, up, toggleBuff } fr
 import { canTargetEnemy, sortEnemyTargets } from '../../../targeting.js';
 import { hasHp } from '../../../damage.js';
 import { COLS } from '../../../constants.js';
+import { hypot } from '../../../detmath.js';
 
 const S1 = 'skchr_ebnhlz_1';
 const S2 = 'skchr_ebnhlz_2';
@@ -116,7 +117,7 @@ function remnantTiles(battle, unit) {
   const rank = new Map();
   foes.forEach((e, i) => { const k = Math.round(e.y) * COLS + Math.round(e.x); if (!rank.has(k)) rank.set(k, i); });
   battle.rng.shuffle(tiles);   // the random order of the last group, and of equal distances [ASSUMED]
-  const dist = (r, c) => { let d = Infinity; for (const e of foes) d = Math.min(d, Math.hypot(e.x - c, e.y - r)); return d; };
+  const dist = (r, c) => { let d = Infinity; for (const e of foes) d = Math.min(d, hypot(e.x - c, e.y - r)); return d; };
   const keyed = tiles.map(([r, c], i) => ({ r, c, i, on: rank.get(r * COLS + c) ?? Infinity, d: dist(r, c) }));
   keyed.sort((a, b) => a.on - b.on || a.d - b.d || a.i - b.i);
   return keyed.map((x) => [x.r, x.c]);