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/buffs.js

@@ -8,6 +8,7 @@
 // Additive mod keys scale with stacks (value × stacks); *Mul keys multiply (value ^ stacks).
 
 import { COLD_ASPD, COLD_FREEZE_DURATION, FREEZE_RES_DOWN, RESIST_DEFAULT, RESIST_PALSY_DECAY } from './constants.js';
+import { powi } from './detmath.js';
 
 /** 抵抗: "麻痹等状态每5秒流失1层" — tick of the resist buff. */
 function resistPalsyDecay({ battle, unit }) {
@@ -200,12 +201,12 @@ export function aggregateMods(buffs) {
         const v = m[k];
         if (typeof v !== 'number' || !Number.isFinite(v)) continue;
         if (k === 'shield') continue;
-        if (k.endsWith('Mul')) mul[k] = (mul[k] ?? 1) * (st === 1 ? v : Math.pow(v, st));
+        if (k.endsWith('Mul')) mul[k] = (mul[k] ?? 1) * (st === 1 ? v : powi(v, st));
         else if ((k === 'dodgePhys' || k === 'dodgeArts') && v > 0) {
           const p = Math.min(1, v);
           const d = dodge[k];
-          if (!d) dodge[k] = { n: st, p, miss: Math.pow(1 - p, st) };
-          else { d.n += st; d.miss *= Math.pow(1 - p, st); }
+          if (!d) dodge[k] = { n: st, p, miss: powi(1 - p, st) };
+          else { d.n += st; d.miss *= powi(1 - p, st); }
         } else {
           add[k] = (add[k] ?? 0) + v * st;
           if (k === 'rangeExtend' && b.persist && b.duration === Infinity) permRangeExtend += v * st;