refactor(core): 애니메이션 컴포저 및 저장 데이터 개선

- CanvasWalkingComposer 정리
- SaveData 모델 확장

lib/src/core/model/save_data.dart

@@ -1,9 +1,15 @@
 import 'dart:collection';
 
+import 'package:asciineverdie/src/core/model/equipment_item.dart';
+import 'package:asciineverdie/src/core/model/equipment_slot.dart';
+import 'package:asciineverdie/src/core/model/monster_grade.dart';
 import 'package:asciineverdie/src/core/util/deterministic_random.dart';
 import 'package:asciineverdie/src/core/model/game_state.dart';
 
-const int kSaveVersion = 2;
+/// 세이브 파일 버전
+/// - v2: 장비 이름만 저장 (레거시)
+/// - v3: 장비 전체 정보 저장 (level, rarity, stats 포함)
+const int kSaveVersion = 3;
 
 class GameSave {
   GameSave({
@@ -79,17 +85,7 @@ class GameSave {
             .toList(),
       },
       'equipment': {
-        'weapon': equipment.weapon,
-        'shield': equipment.shield,
-        'helm': equipment.helm,
-        'hauberk': equipment.hauberk,
-        'brassairts': equipment.brassairts,
-        'vambraces': equipment.vambraces,
-        'gauntlets': equipment.gauntlets,
-        'gambeson': equipment.gambeson,
-        'cuisses': equipment.cuisses,
-        'greaves': equipment.greaves,
-        'sollerets': equipment.sollerets,
+        'items': equipment.items.map((e) => e.toJson()).toList(),
         'bestIndex': equipment.bestIndex,
       },
       'skills': skillBook.skills
@@ -106,6 +102,8 @@ class GameSave {
           'type': progress.currentTask.type.name,
           'monsterBaseName': progress.currentTask.monsterBaseName,
           'monsterPart': progress.currentTask.monsterPart,
+          'monsterLevel': progress.currentTask.monsterLevel,
+          'monsterGrade': progress.currentTask.monsterGrade?.name,
         },
         'plotStages': progress.plotStageCount,
         'questCount': progress.questCount,
@@ -183,20 +181,7 @@ class GameSave {
             )
             .toList(),
       ),
-      equipment: Equipment.fromStrings(
-        weapon: equipmentJson['weapon'] as String? ?? 'Keyboard',
-        shield: equipmentJson['shield'] as String? ?? '',
-        helm: equipmentJson['helm'] as String? ?? '',
-        hauberk: equipmentJson['hauberk'] as String? ?? '',
-        brassairts: equipmentJson['brassairts'] as String? ?? '',
-        vambraces: equipmentJson['vambraces'] as String? ?? '',
-        gauntlets: equipmentJson['gauntlets'] as String? ?? '',
-        gambeson: equipmentJson['gambeson'] as String? ?? '',
-        cuisses: equipmentJson['cuisses'] as String? ?? '',
-        greaves: equipmentJson['greaves'] as String? ?? '',
-        sollerets: equipmentJson['sollerets'] as String? ?? '',
-        bestIndex: equipmentJson['bestIndex'] as int? ?? 0,
-      ),
+      equipment: _equipmentFromJson(equipmentJson, json['version'] as int? ?? 2),
       skillBook: SkillBook(
         skills: skillsJson
             .map(
@@ -289,11 +274,23 @@ TaskInfo _taskInfoFromJson(Map<String, dynamic> json) {
     (t) => t.name == typeName,
     orElse: () => TaskType.neutral,
   );
+
+  // monsterGrade 파싱
+  final gradeName = json['monsterGrade'] as String?;
+  final monsterGrade = gradeName != null
+      ? MonsterGrade.values.firstWhere(
+          (g) => g.name == gradeName,
+          orElse: () => MonsterGrade.normal,
+        )
+      : null;
+
   return TaskInfo(
     caption: json['caption'] as String? ?? '',
     type: type,
     monsterBaseName: json['monsterBaseName'] as String?,
     monsterPart: json['monsterPart'] as String?,
+    monsterLevel: json['monsterLevel'] as int?,
+    monsterGrade: monsterGrade,
   );
 }
 
@@ -315,3 +312,46 @@ QuestMonsterInfo? _questMonsterFromJson(Map<String, dynamic>? json) {
     monsterIndex: json['index'] as int? ?? -1,
   );
 }
+
+/// 장비 데이터 역직렬화 (버전별 분기 처리)
+///
+/// - v2 이하: 레거시 문자열 기반 (이름만 저장)
+/// - v3 이상: 전체 EquipmentItem 정보 저장
+Equipment _equipmentFromJson(Map<String, dynamic> json, int version) {
+  // v3 이상: 새로운 형식 (items 배열)
+  if (version >= 3 && json['items'] != null) {
+    final itemsList = json['items'] as List<dynamic>;
+    final items = <EquipmentItem>[];
+
+    for (var i = 0; i < Equipment.slotCount; i++) {
+      if (i < itemsList.length) {
+        final itemJson = itemsList[i] as Map<String, dynamic>;
+        items.add(EquipmentItem.fromJson(itemJson));
+      } else {
+        // 누락된 슬롯은 빈 아이템으로 채움
+        items.add(EquipmentItem.empty(EquipmentSlot.values[i]));
+      }
+    }
+
+    return Equipment(
+      items: items,
+      bestIndex: json['bestIndex'] as int? ?? 0,
+    );
+  }
+
+  // v2 이하: 레거시 형식 (문자열 기반)
+  return Equipment.fromStrings(
+    weapon: json['weapon'] as String? ?? 'Keyboard',
+    shield: json['shield'] as String? ?? '',
+    helm: json['helm'] as String? ?? '',
+    hauberk: json['hauberk'] as String? ?? '',
+    brassairts: json['brassairts'] as String? ?? '',
+    vambraces: json['vambraces'] as String? ?? '',
+    gauntlets: json['gauntlets'] as String? ?? '',
+    gambeson: json['gambeson'] as String? ?? '',
+    cuisses: json['cuisses'] as String? ?? '',
+    greaves: json['greaves'] as String? ?? '',
+    sollerets: json['sollerets'] as String? ?? '',
+    bestIndex: json['bestIndex'] as int? ?? 0,
+  );
+}