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.js

@@ -116,6 +116,7 @@ import { REFLECTION_KITS } from './enemies/reflection.js';
 import { FLY_KITS } from './enemies/fly.js';
 import { SPECIAL_KITS } from './enemies/special.js';
 import { LEADER_KITS } from './enemies/leaders.js';
+import { hypot } from '../detmath.js';
 
 export {
   EROSION, EROSION_BURST, HUSK_REBIRTH, nthOf, abOf, attach, T, silenced, canCast, elem, hurt, alliesInTiles,
@@ -312,7 +313,7 @@ function chaliceShare(b, c) {
   for (const o of b.enemies) {
     if (!o.alive || o === t || o.defId !== 'enemy_1430_lrrook' || !o.mem.ab) continue;
     const a = o.mem.ab.list[0];
-    if (!a || !(a.share > 0) || Math.hypot(o.x - t.x, o.y - t.y) > a.r) continue;
+    if (!a || !(a.share > 0) || hypot(o.x - t.x, o.y - t.y) > a.r) continue;
     const part = c.dmg.amount * a.share;
     c.dmg.amount -= part;
     // a 无来源 burst's share stays 无来源, credited like the burst (damage.js)