feat: 초기 커밋

- Progress Quest 6.4 Flutter 포팅 프로젝트
- 게임 루프, 상태 관리, UI 구현
- 캐릭터 생성, 인벤토리, 장비, 주문 시스템
- 시장/판매/구매 메커니즘

lib/src/core/engine/game_mutations.dart

@@ -0,0 +1,86 @@
+import 'package:askiineverdie/src/core/model/equipment_slot.dart';
+import 'package:askiineverdie/src/core/model/game_state.dart';
+import 'package:askiineverdie/src/core/model/pq_config.dart';
+import 'package:askiineverdie/src/core/util/pq_logic.dart' as pq_logic;
+
+/// Game state mutations that mirror the original PQ win/reward logic.
+class GameMutations {
+  const GameMutations(this.config);
+
+  final PqConfig config;
+
+  GameState winEquip(GameState state, int level, EquipmentSlot slot) {
+    final rng = state.rng;
+    final name = pq_logic.winEquip(config, rng, level, slot);
+    final equip = state.equipment;
+    final updatedEquip = switch (slot) {
+      EquipmentSlot.weapon => equip.copyWith(
+        weapon: name,
+        bestIndex: EquipmentSlot.weapon.index,
+      ),
+      EquipmentSlot.shield => equip.copyWith(
+        shield: name,
+        bestIndex: EquipmentSlot.shield.index,
+      ),
+      EquipmentSlot.armor => equip.copyWith(
+        armor: name,
+        bestIndex: EquipmentSlot.armor.index,
+      ),
+    };
+    return state.copyWith(rng: rng, equipment: updatedEquip);
+  }
+
+  GameState winStat(GameState state) {
+    final updatedStats = pq_logic.winStat(state.stats, state.rng);
+    return state.copyWith(rng: state.rng, stats: updatedStats);
+  }
+
+  GameState winSpell(GameState state, int wisdom, int level) {
+    final result = pq_logic.winSpell(config, state.rng, wisdom, level);
+    final parts = result.split('|');
+    final name = parts[0];
+    final rank = parts.length > 1 ? parts[1] : 'I';
+
+    final spells = [...state.spellBook.spells];
+    final index = spells.indexWhere((s) => s.name == name);
+    if (index >= 0) {
+      spells[index] = spells[index].copyWith(rank: rank);
+    } else {
+      spells.add(SpellEntry(name: name, rank: rank));
+    }
+
+    return state.copyWith(
+      rng: state.rng,
+      spellBook: state.spellBook.copyWith(spells: spells),
+    );
+  }
+
+  GameState winItem(GameState state) {
+    final rng = state.rng;
+    final result = pq_logic.winItem(config, rng, state.inventory.items.length);
+    final items = [...state.inventory.items];
+
+    if (result.isEmpty) {
+      // Duplicate an existing item if possible.
+      if (items.isNotEmpty) {
+        final pickIndex = rng.nextInt(items.length);
+        final picked = items[pickIndex];
+        items[pickIndex] = picked.copyWith(count: picked.count + 1);
+      }
+    } else {
+      final existing = items.indexWhere((e) => e.name == result);
+      if (existing >= 0) {
+        items[existing] = items[existing].copyWith(
+          count: items[existing].count + 1,
+        );
+      } else {
+        items.add(InventoryEntry(name: result, count: 1));
+      }
+    }
+
+    return state.copyWith(
+      rng: rng,
+      inventory: state.inventory.copyWith(items: items),
+    );
+  }
+}