feat: show 99.5 percent score achievement probability

src/lib/engine/score-probability.test.ts

@@ -100,6 +100,7 @@ test('확정 발동이면 모든 달성 확률이 100%다', () => {
   );
   assert.deepEqual(result, {
     maximum: 1,
+    atLeast995Percent: 1,
     atLeast99Percent: 1,
     atLeast95Percent: 1,
     samples: 1_000
@@ -134,3 +135,18 @@ test('미발동 토글 시 현재 최고점 기준으로 확률을 계산하고
   assert.deepEqual(calculateMaximumScoreProbabilityTimeline(cards, {}, chart([1.1]), options), [1]);
   assert.equal(estimateScoreAchievementProbabilities(cards, {}, chart([1.1]), options).maximum, 1);
 });
+
+
+test('99.5% 경계 점수를 포함하고 99% 이상 점수와 구분한다', () => {
+  const estimate = (fallbackBoost: number) => estimateScoreAchievementProbabilities(
+    [card('strong', 100, 50), card('fallback', fallbackBoost, 100)],
+    { strong: 0, fallback: 0 },
+    chart([1.1]),
+    { perfectNoteScore: 10_000, sampleCount: 25_000, seed: 7 }
+  );
+  // 최고점 20,000점에서 19,900점은 포함하고 19,850점은 제외한다.
+  assert.equal(estimate(99).atLeast995Percent, 1);
+  const below = estimate(98.5);
+  assert.ok(Math.abs(below.atLeast995Percent - 0.5) < 0.02);
+  assert.equal(below.atLeast99Percent, 1);
+});