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-jesca2.js

@@ -58,6 +58,7 @@
 import { num, talentBb, traitBb, moduleOn, skillRec, batMod, up, giveSp, installReveal } from '../shared/tier1.js';
 import { offsetTile, dirFromDelta, dirVec } from '../../../dir.js';
 import { isHpLoss } from '../../../damage.js';
+import { hypot } from '../../../detmath.js';
 
 const S1 = 'skchr_jesca2_1';
 const S2 = 'skchr_jesca2_2';
@@ -182,7 +183,7 @@ function fireBomb(battle, unit, b3) {
   };
   (unit.mem.jescaShells ??= []).push(bomb);
   unit.atkCd = unit.s.interval;   // the shell is her attack: the timer restarts [ASSUMED]
-  battle.fx('bombardShell', { x: bomb.tx, y: bomb.ty, id: unit.id, r: bomb.radius, t: Math.hypot(bomb.tx - bomb.x, bomb.ty - bomb.y) / BOMB_SPEED });
+  battle.fx('bombardShell', { x: bomb.tx, y: bomb.ty, id: unit.id, r: bomb.radius, t: hypot(bomb.tx - bomb.x, bomb.ty - bomb.y) / BOMB_SPEED });
 }
 
 /** Move the shells one tick; a shell touching an enemy or reaching its end point explodes. */
@@ -192,7 +193,7 @@ function flyShells(battle, unit, dt) {
   const keep = [];
   for (const s of list) {
     const dx = s.tx - s.x, dy = s.ty - s.y;
-    const d = Math.hypot(dx, dy);
+    const d = hypot(dx, dy);
     const step = BOMB_SPEED * dt;
     let hit = battle.foesInRadius(s.x, s.y, BOMB_HIT_RADIUS).length > 0;
     if (!hit) {