refactor(potion): 물약 자동 사용 조건 변경

- 임계치 기반 → 소모량 기반 조건 전환
- HP/MP 소모량 >= 물약 회복량일 때 사용
- emergencyHpThreshold, emergencyMpThreshold 상수 제거
- 우선순위 HP > MP 유지

lib/src/core/engine/combat_tick_service.dart

@@ -265,79 +265,73 @@ class CombatTickService {
       return null;
     }
 
-    // 우선순위 1: HP 물약 (HP <= 30%)
-    final hpRatio = playerStats.hpCurrent / playerStats.hpMax;
-    if (hpRatio <= PotionService.emergencyHpThreshold) {
-      final hpPotion = potionService.selectEmergencyHpPotion(
+    // 우선순위 1: HP 물약 (소모된 HP >= 물약 회복량)
+    final hpPotion = potionService.selectEmergencyHpPotion(
+      currentHp: playerStats.hpCurrent,
+      maxHp: playerStats.hpMax,
+      inventory: potionInventory,
+      playerLevel: playerLevel,
+    );
+
+    if (hpPotion != null) {
+      final result = potionService.usePotion(
+        potionId: hpPotion.id,
+        inventory: potionInventory,
         currentHp: playerStats.hpCurrent,
         maxHp: playerStats.hpMax,
-        inventory: potionInventory,
-        playerLevel: playerLevel,
+        currentMp: playerStats.mpCurrent,
+        maxMp: playerStats.mpMax,
       );
 
-      if (hpPotion != null) {
-        final result = potionService.usePotion(
-          potionId: hpPotion.id,
-          inventory: potionInventory,
-          currentHp: playerStats.hpCurrent,
-          maxHp: playerStats.hpMax,
-          currentMp: playerStats.mpCurrent,
-          maxMp: playerStats.mpMax,
+      if (result.success) {
+        return (
+          playerStats: playerStats.copyWith(hpCurrent: result.newHp),
+          lastPotionUsedMs: timestamp,
+          potionInventory: result.newInventory!,
+          events: [
+            CombatEvent.playerPotion(
+              timestamp: timestamp,
+              potionName: hpPotion.name,
+              healAmount: result.healedAmount,
+              isHp: true,
+            ),
+          ],
         );
-
-        if (result.success) {
-          return (
-            playerStats: playerStats.copyWith(hpCurrent: result.newHp),
-            lastPotionUsedMs: timestamp,
-            potionInventory: result.newInventory!,
-            events: [
-              CombatEvent.playerPotion(
-                timestamp: timestamp,
-                potionName: hpPotion.name,
-                healAmount: result.healedAmount,
-                isHp: true,
-              ),
-            ],
-          );
-        }
       }
     }
 
-    // 우선순위 2: MP 물약 (MP <= 50%)
-    final mpRatio = playerStats.mpCurrent / playerStats.mpMax;
-    if (mpRatio <= PotionService.emergencyMpThreshold) {
-      final mpPotion = potionService.selectEmergencyMpPotion(
+    // 우선순위 2: MP 물약 (소모된 MP >= 물약 회복량)
+    final mpPotion = potionService.selectEmergencyMpPotion(
+      currentMp: playerStats.mpCurrent,
+      maxMp: playerStats.mpMax,
+      inventory: potionInventory,
+      playerLevel: playerLevel,
+    );
+
+    if (mpPotion != null) {
+      final result = potionService.usePotion(
+        potionId: mpPotion.id,
+        inventory: potionInventory,
+        currentHp: playerStats.hpCurrent,
+        maxHp: playerStats.hpMax,
         currentMp: playerStats.mpCurrent,
         maxMp: playerStats.mpMax,
-        inventory: potionInventory,
-        playerLevel: playerLevel,
       );
 
-      if (mpPotion != null) {
-        final result = potionService.usePotion(
-          potionId: mpPotion.id,
-          inventory: potionInventory,
-          currentHp: playerStats.hpCurrent,
-          maxHp: playerStats.hpMax,
-          currentMp: playerStats.mpCurrent,
-          maxMp: playerStats.mpMax,
+      if (result.success) {
+        return (
+          playerStats: playerStats.copyWith(mpCurrent: result.newMp),
+          lastPotionUsedMs: timestamp,
+          potionInventory: result.newInventory!,
+          events: [
+            CombatEvent.playerPotion(
+              timestamp: timestamp,
+              potionName: mpPotion.name,
+              healAmount: result.healedAmount,
+              isHp: false,
+            ),
+          ],
         );
-
-        if (result.success) {
-          return (
-            playerStats: playerStats.copyWith(mpCurrent: result.newMp),
-            lastPotionUsedMs: timestamp,
-            potionInventory: result.newInventory!,
-            events: [
-              CombatEvent.playerPotion(
-                timestamp: timestamp,
-                potionName: mpPotion.name,
-                healAmount: result.healedAmount,
-                isHp: false,
-              ),
-            ],
-          );
-        }
       }
     }
 

lib/src/core/engine/potion_service.dart

@@ -13,12 +13,6 @@ class PotionService {
   /// 글로벌 물약 쿨타임 (1배속 기준 3초)
   static const int globalPotionCooldownMs = 3000;
 
-  /// 긴급 물약 사용 HP 임계치 (30%)
-  static const double emergencyHpThreshold = 0.30;
-
-  /// 긴급 물약 사용 MP 임계치 (50%)
-  static const double emergencyMpThreshold = 0.50;
-
   // ============================================================================
   // 물약 사용 가능 여부
   // ============================================================================
@@ -104,7 +98,7 @@ class PotionService {
 
   /// 긴급 HP 물약 선택
   ///
-  /// HP가 임계치 이하일 때 사용할 최적의 물약 선택
+  /// 소모된 HP >= 물약 회복량이면 사용할 최적의 물약 선택
   /// [currentHp] 현재 HP
   /// [maxHp] 최대 HP
   /// [inventory] 물약 인벤토리
@@ -115,9 +109,8 @@ class PotionService {
     required PotionInventory inventory,
     required int playerLevel,
   }) {
-    // 임계치 체크
-    final hpRatio = currentHp / maxHp;
-    if (hpRatio > emergencyHpThreshold) return null;
+    final hpLost = maxHp - currentHp;
+    if (hpLost <= 0) return null;
 
     // 적정 티어 계산
     final targetTier = PotionData.tierForLevel(playerLevel);
@@ -126,7 +119,10 @@ class PotionService {
     for (var tier = targetTier; tier >= 1; tier--) {
       final potion = PotionData.getHpPotionByTier(tier);
       if (potion != null && inventory.hasPotion(potion.id)) {
-        return potion;
+        final healAmount = potion.calculateHeal(maxHp);
+        if (hpLost >= healAmount) {
+          return potion;
+        }
       }
     }
 
@@ -134,7 +130,10 @@ class PotionService {
     for (var tier = targetTier + 1; tier <= 5; tier++) {
       final potion = PotionData.getHpPotionByTier(tier);
       if (potion != null && inventory.hasPotion(potion.id)) {
-        return potion;
+        final healAmount = potion.calculateHeal(maxHp);
+        if (hpLost >= healAmount) {
+          return potion;
+        }
       }
     }
 
@@ -143,16 +142,15 @@ class PotionService {
 
   /// 긴급 MP 물약 선택
   ///
-  /// MP가 임계치 이하일 때 사용할 최적의 물약 선택
+  /// 소모된 MP >= 물약 회복량이면 사용할 최적의 물약 선택
   Potion? selectEmergencyMpPotion({
     required int currentMp,
     required int maxMp,
     required PotionInventory inventory,
     required int playerLevel,
   }) {
-    // 임계치 체크
-    final mpRatio = currentMp / maxMp;
-    if (mpRatio > emergencyMpThreshold) return null;
+    final mpLost = maxMp - currentMp;
+    if (mpLost <= 0) return null;
 
     // 적정 티어 계산
     final targetTier = PotionData.tierForLevel(playerLevel);
@@ -161,7 +159,10 @@ class PotionService {
     for (var tier = targetTier; tier >= 1; tier--) {
       final potion = PotionData.getMpPotionByTier(tier);
       if (potion != null && inventory.hasPotion(potion.id)) {
-        return potion;
+        final healAmount = potion.calculateHeal(maxMp);
+        if (mpLost >= healAmount) {
+          return potion;
+        }
       }
     }
 
@@ -169,7 +170,10 @@ class PotionService {
     for (var tier = targetTier + 1; tier <= 5; tier++) {
       final potion = PotionData.getMpPotionByTier(tier);
       if (potion != null && inventory.hasPotion(potion.id)) {
-        return potion;
+        final healAmount = potion.calculateHeal(maxMp);
+        if (mpLost >= healAmount) {
+          return potion;
+        }
       }
     }