feat(engine): 엔진 서비스 개선 및 테스트 캐릭터 서비스 추가

- ProgressService 로직 개선
- RewardService 확장
- CombatCalculator, ItemService 정리
- TestCharacterService 추가

lib/src/core/engine/reward_service.dart

@@ -1,25 +1,82 @@
 import 'package:asciineverdie/src/core/engine/game_mutations.dart';
+import 'package:asciineverdie/src/core/engine/item_service.dart';
+import 'package:asciineverdie/src/core/engine/shop_service.dart';
+import 'package:asciineverdie/src/core/model/equipment_slot.dart';
 import 'package:asciineverdie/src/core/model/game_state.dart';
-import 'package:asciineverdie/src/core/util/pq_logic.dart';
+import 'package:asciineverdie/src/core/model/pq_config.dart';
+import 'package:asciineverdie/src/core/util/pq_logic.dart' as pq_logic;
 
 /// Applies quest/act rewards to the GameState using shared RNG.
 class RewardService {
-  RewardService(this.mutations);
+  RewardService(this.mutations, this.config);
 
   final GameMutations mutations;
+  final PqConfig config;
 
-  GameState applyReward(GameState state, RewardKind reward) {
+  GameState applyReward(GameState state, pq_logic.RewardKind reward) {
     switch (reward) {
-      case RewardKind.spell:
+      case pq_logic.RewardKind.spell:
         return mutations.winSpell(state, state.stats.wis, state.traits.level);
-      case RewardKind.equip:
-        // 원본 Main.pas:797 - Random(Equips.Items.Count) (11개 슬롯)
-        final slotIndex = state.rng.nextInt(Equipment.slotCount);
-        return mutations.winEquipByIndex(state, state.traits.level, slotIndex);
-      case RewardKind.stat:
+      case pq_logic.RewardKind.equip:
+        return _applyEquipReward(state);
+      case pq_logic.RewardKind.stat:
         return mutations.winStat(state);
-      case RewardKind.item:
+      case pq_logic.RewardKind.item:
         return mutations.winItem(state);
     }
   }
+
+  /// 장비 보상 처리 (개선된 로직)
+  ///
+  /// - 빈 슬롯: 무조건 장착
+  /// - 기존 장비 있음: 점수 비교 → 업그레이드만 / 다운그레이드 시 판매
+  GameState _applyEquipReward(GameState state) {
+    final slotIndex = state.rng.nextInt(Equipment.slotCount);
+    final slot = EquipmentSlot.values[slotIndex];
+    final currentItem = state.equipment.getItemByIndex(slotIndex);
+    final level = state.traits.level;
+
+    // 새 장비 생성
+    final itemService = ItemService(rng: state.rng);
+    final name = pq_logic.winEquip(config, state.rng, level, slotIndex);
+    final newItem = itemService.generateEquipment(
+      name: name,
+      slot: slot,
+      level: level,
+    );
+
+    // 빈 슬롯이면 무조건 장착
+    if (currentItem.isEmpty) {
+      return state.copyWith(
+        rng: state.rng,
+        equipment: state.equipment
+            .setItemByIndex(slotIndex, newItem)
+            .copyWith(bestIndex: slotIndex),
+      );
+    }
+
+    // 점수 비교
+    final currentScore = ItemService.calculateEquipmentScore(currentItem);
+    final newScore = ItemService.calculateEquipmentScore(newItem);
+
+    if (newScore > currentScore) {
+      // 업그레이드: 새 장비 장착
+      return state.copyWith(
+        rng: state.rng,
+        equipment: state.equipment
+            .setItemByIndex(slotIndex, newItem)
+            .copyWith(bestIndex: slotIndex),
+      );
+    } else {
+      // 다운그레이드: 새 장비 판매 (골드로 변환)
+      final shopService = ShopService(rng: state.rng);
+      final sellPrice = shopService.calculateSellPrice(newItem);
+      return state.copyWith(
+        rng: state.rng,
+        inventory: state.inventory.copyWith(
+          gold: state.inventory.gold + sellPrice,
+        ),
+      );
+    }
+  }
 }