feat: support every song difficulty including Easy and Normal

src/routes/combination/+page.svelte

@@ -41,7 +41,7 @@
   export let eventMode = false;
 
   type CardRow = (typeof cardSummary.cards)[number];
-  type DifficultyKey = 'hard' | 'expert';
+  import { difficulties, difficultyLabel, isDifficulty, type DifficultyKey } from '$lib/data/difficulty.ts';
   type CollectionState = Record<string, { owned?: boolean; awakening?: number }>;
   type MemberBoards = Record<string, string[]>;
   type BoardCards = Record<string, Record<string, string>>;
@@ -370,7 +370,7 @@
   function applySavedState(state: Partial<SavedState>): void {
     if (state.schemaVersion !== 1) throw new Error('Unsupported preset');
     if (typeof state.songId === 'string' && songs.some((song) => song.id === state.songId)) selectedSongId = state.songId;
-    if (state.difficulty === 'hard' || state.difficulty === 'expert') difficulty = state.difficulty;
+    if (isDifficulty(state.difficulty)) difficulty = state.difficulty;
     fixedCardIds = Array.from({ length: 4 }, (_, index) => cardById.has(state.fixedCardIds?.[index] ?? '') ? state.fixedCardIds![index] : '');
     candidateAwakening = normalizeAwakening(state.awakening);
     candidateGenerationBonus = typeof state.candidateGenerationBonus === 'number' && Number.isFinite(state.candidateGenerationBonus)
@@ -422,7 +422,7 @@
     return {
       schemaVersion: 2,
       songId: typeof state.songId === 'string' ? state.songId : '',
-      difficulty: state.difficulty === 'hard' ? 'hard' : 'expert',
+      difficulty: isDifficulty(state.difficulty) ? state.difficulty : 'expert',
       cardIds: cards.map((card) => card.id),
       awakenings: cards.map((_, index) => Number.isFinite(state.awakenings?.[index]) ? normalizeAwakening(state.awakenings?.[index]) : 0),
       fixedCooldownReductions: cards.map((_, index) => normalizeFixedReduction(state.fixedCooldownReductions?.[index])),
@@ -1140,7 +1140,7 @@
         <div><span>00</span><h2 id="baseline-title">기준 조합</h2></div>
         <strong>배치 분석 저장값</strong>
       </div>
-      <p class="baseline-condition">{baselineChartMetadata?.title} · {baselineState.difficulty === 'expert' ? 'Expert' : 'Hard'}</p>
+      <p class="baseline-condition">{baselineChartMetadata?.title} · {difficultyLabel(baselineState.difficulty)}</p>
       <div class="baseline-members">
         {#each baselineResult?.formationOrder ?? baselineState.cardIds as cardId, slot}
           <div><span>{slot + 1}</span><strong>{baselineCardLabel(cardId)}</strong></div>
@@ -1164,7 +1164,7 @@
     <div class="section-title"><div><span>01</span><h2 id="conditions-title">탐색 조건</h2></div><strong>{ownedCardsOnly ? (eventMode ? '보유 이벤트 후보 대상' : '보유 5성 대상') : (eventMode ? '5성 + 대상 멤버 전 레어리티' : '5성 전체 대상')}</strong></div>
     <div class="song-fields">
       <div class="song-picker-field"><SongPicker {charts} {difficulty} bind:value={selectedSongId} on:change={() => result = null} /></div>
-      <label>난이도<select bind:value={difficulty} on:change={() => result = null}><option value="expert">Expert</option><option value="hard">Hard</option></select></label>
+      <label>난이도<select bind:value={difficulty} on:change={() => result = null}>{#each difficulties as value}<option {value}>{difficultyLabel(value)}</option>{/each}</select></label>
       <div class="chart-meta"><span>길이 {selectedChart?.durationSeconds ?? 0}초</span><span>노트 {selectedChart?.totalNotes?.toLocaleString('ko-KR') ?? 0}개</span><span>점수 계수 · {scoreCalibrationLabel}</span></div>
     </div>
     <div class="candidate-fields">