feat(card-frames): 보상 등급 가중 추첨 70/25/5 (Lua + JS 미러 rarityForRoll·경계 테스트)

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

tools/balance/sim-balance.mjs

@@ -29,6 +29,13 @@ export function shuffle(arr, rng) {
 
 // 공격 피해 공식 — Lua CalcPlayerAttack(힘·약화) + DealDamageToTarget(취약)과 동기화.
 // floor((base + str) * (weak>0 ? 0.75 : 1)) → floor(... * (vulnOnTarget>0 ? 1.5 : 1))
+// 보상 카드 등급 추첨 (Lua OfferReward 미러) — roll ∈ 1..100, normal 70 / unique 25 / legend 5
+export function rarityForRoll(roll) {
+  if (roll > 95) return 'legend';
+  if (roll > 70) return 'unique';
+  return 'normal';
+}
+
 export function calcAttack(base, str, weak, vulnOnTarget) {
   let dmg = base + str;
   if (weak > 0) dmg = Math.floor(dmg * 0.75);

tools/balance/sim-balance.test.mjs

@@ -1,9 +1,18 @@
 import { test } from 'node:test';
 import assert from 'node:assert/strict';
 import {
-  mulberry32, applyDamage, chooseAction, chooseTarget, simulateCombat, runBatch, calcAttack,
+  mulberry32, applyDamage, chooseAction, chooseTarget, simulateCombat, runBatch, calcAttack, rarityForRoll,
 } from './sim-balance.mjs';
 
+test('rarityForRoll: 70/25/5 경계 (Lua OfferReward 미러)', () => {
+  assert.equal(rarityForRoll(1), 'normal');
+  assert.equal(rarityForRoll(70), 'normal');
+  assert.equal(rarityForRoll(71), 'unique');
+  assert.equal(rarityForRoll(95), 'unique');
+  assert.equal(rarityForRoll(96), 'legend');
+  assert.equal(rarityForRoll(100), 'legend');
+});
+
 test('applyDamage: 방어 우선 차감 후 hp', () => {
   assert.deepEqual(applyDamage(80, 0, 10), { hp: 70, block: 0 });
   assert.deepEqual(applyDamage(80, 5, 10), { hp: 75, block: 0 });