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-haruka.js

@@ -50,6 +50,7 @@
 import { num, up, traitBb, talentBb, skillRec, batMod, giveSp, protectMods } from '../shared/tier1.js';
 import { absoluteRangeKeys } from '../../../targeting.js';
 import { COLS } from '../../../constants.js';
+import { hypot } from '../../../detmath.js';
 
 const S1 = 'skchr_haruka_1';
 const S2 = 'skchr_haruka_2';
@@ -217,7 +218,7 @@ export default {
             if (c.source !== unit || c.opts?.regen || !skillOn(unit, S2) || !(c.amount > 0) || !(scale > 0) || !n) return;
             const t = c.target;
             const foes = battle.foesInRadius(t.x, t.y, r);
-            foes.sort((x, y) => Math.hypot(x.x - t.x, x.y - t.y) - Math.hypot(y.x - t.x, y.y - t.y) || x.spawnSeq - y.spawnSeq);
+            foes.sort((x, y) => hypot(x.x - t.x, x.y - t.y) - hypot(y.x - t.x, y.y - t.y) || x.spawnSeq - y.spawnSeq);
             const amount = c.amount * scale;
             for (const e of foes.slice(0, n)) battle.dealDamage(unit, e, { amount, type: 'arts', isSkill: true, tags: ['skill', 'haruka:s2'] });
             if (foes.length) battle.fx('aoe', { x: t.x, y: t.y, radius: r, id: unit.id, skill: 'haruka:s2' });