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-radian.js

@@ -64,6 +64,7 @@ import { acquireTargets } from '../../../ai.js';
 import { aggregateMods } from '../../../buffs.js';
 import { dirVec } from '../../../dir.js';
 import { COLS } from '../../../constants.js';
+import { hypot } from '../../../detmath.js';
 
 const S1 = 'skchr_radian_1';
 const S2 = 'skchr_radian_2';
@@ -160,7 +161,7 @@ function flyBullets(battle, t, dt) {
     const hit = () => {
       const near = battle.foesInRadius(b.x, b.y, BULLET_RADIUS).filter((e) => e.alive && !e.isFlying);
       if (!near.length) return false;
-      near.sort((p, q) => Math.hypot(p.x - b.x, p.y - b.y) - Math.hypot(q.x - b.x, q.y - b.y) || p.spawnSeq - q.spawnSeq);
+      near.sort((p, q) => hypot(p.x - b.x, p.y - b.y) - hypot(q.x - b.x, q.y - b.y) || p.spawnSeq - q.spawnSeq);
       battle.dealDamage(t, near[0], { amount: b.atk, type: 'phys', isAttack: true, tags: [TAG_BULLET] });
       return true;
     };