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/enemies/invisible.js

@@ -4,6 +4,7 @@
 import { canTargetAlly, enemyStealthed } from '../../targeting.js';
 import { T, elem, hurt, targetsNear, byPriority, auraBuff } from './helpers.js';
 import { stealth, onHitStatus, skill, kitStealth } from './archetypes.js';
+import { hypot } from '../../detmath.js';
 
 // ---------------------------------------------------------------------------------------------------------------
 // constants (numbers that exist nowhere in the data)
@@ -20,8 +21,8 @@ const CROSS_REACH = 6, CROSS_SKILL = 2.5, CROSS_CHARGE = 1.4;
 
 function kitCrossbow(ab) {
   const s = ab.sk.CrossAttack;
-  const aligned = (b, e) => b.allies().filter((u) => canTargetAlly(e, u, true) && (Math.abs(u.y - e.y) < 0.5 || Math.abs(u.x - e.x) < 0.5) && Math.hypot(u.x - e.x, u.y - e.y) <= CROSS_REACH);
-  const nearest = (b, e, l) => l.sort((p, q) => Math.hypot(p.x - e.x, p.y - e.y) - Math.hypot(q.x - e.x, q.y - e.y))[0];
+  const aligned = (b, e) => b.allies().filter((u) => canTargetAlly(e, u, true) && (Math.abs(u.y - e.y) < 0.5 || Math.abs(u.x - e.x) < 0.5) && hypot(u.x - e.x, u.y - e.y) <= CROSS_REACH);
+  const nearest = (b, e, l) => l.sort((p, q) => hypot(p.x - e.x, p.y - e.y) - hypot(q.x - e.x, q.y - e.y))[0];
   // PRTS 重弩突袭者: 天赋 "隐匿（被阻挡，主动攻击期间均可解除）"; 直击 "蓄力1.4s后向目标方向发射1支弩箭，对击中的首个目标造成攻击力100%
   // 的法术伤害与5s晕眩 ※技能持续2.5s": revealed for the whole skill, the bolt leaves CROSS_CHARGE s in — at the nearest unit still
   // in line in the aimed direction; it stands meanwhile [ASSUMED], and a stun / silence or its death before the release
@@ -108,7 +109,7 @@ function kitShadowBlade(ab) {
     tick(b, e) {
       const partner = b.enemiesInRadius(e.x, e.y, 3).find((o) => /enemy_1174_duholy/.test(o.defId));
       const r = partner && partner.mem.ab ? (T(partner.mem.ab, 'traitAbility.range_radius') ?? 1.1) : 1.1;
-      if (partner && Math.hypot(partner.x - e.x, partner.y - e.y) <= r + 1e-9 && e.base.bat > 0) auraBuff(b, e, 'ab:shadowSync', 0.5, { batPct: bat / e.base.bat });
+      if (partner && hypot(partner.x - e.x, partner.y - e.y) <= r + 1e-9 && e.base.bat > 0) auraBuff(b, e, 'ab:shadowSync', 0.5, { batPct: bat / e.base.bat });
     },
   }];
 }