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/shared/tier6.js

@@ -111,6 +111,7 @@
 import { absoluteRangeKeys } from '../../../targeting.js';
 import { COLS, ROWS, PULL_STOP_RADIUS } from '../../../constants.js';
 import { hasHp } from '../../../damage.js';
+import { hypot } from '../../../detmath.js';
 
 // ------------------------------------------------------------------------------------------------------------------
 // helpers
@@ -237,7 +238,7 @@ function bestTile(battle, tiles) {
   let best = tiles[0], bd = Infinity;
   for (const t of tiles) {
     let d = Infinity;
-    for (const e of en) d = Math.min(d, Math.hypot(e.x - t[1], e.y - t[0]));
+    for (const e of en) d = Math.min(d, hypot(e.x - t[1], e.y - t[0]));
     if (d < bd - 1e-9) { bd = d; best = t; }
   }
   return best;