feat(state): coordinate booster use with inventory in the session

lib/state/game_session_notifier.dart

@@ -2,12 +2,15 @@ import 'package:flutter_riverpod/flutter_riverpod.dart';
 
 import '../game/engine/game_engine.dart';
 import '../game/engine/piece_generator.dart';
+import '../game/models/booster.dart';
 import '../game/models/grid.dart';
 import '../game/models/objective.dart';
 import '../game/models/piece.dart';
 import '../game/models/stage.dart';
 import 'providers.dart';
 
+enum BoosterUseResult { success, noBooster, invalidTarget }
+
 /// Immutable snapshot of one engine moment; the only game state the UI sees.
 class GameViewState {
   const GameViewState({
@@ -117,6 +120,41 @@ class GameSessionNotifier extends Notifier<GameViewState?> {
     _publish(lastPlacement: null);
   }
 
+  Future<BoosterUseResult> useHammer(int x, int y) =>
+      _useBooster(BoosterType.hammer, () {
+        final engine = _engine;
+        if (engine == null) return false;
+        return engine.useHammer(x, y);
+      });
+
+  Future<BoosterUseResult> useShuffle() =>
+      _useBooster(BoosterType.shuffle, () {
+        final engine = _engine;
+        if (engine == null) return false;
+        return engine.useShuffle();
+      });
+
+  Future<BoosterUseResult> useLineBomb({int? row, int? col}) =>
+      _useBooster(BoosterType.lineBomb, () {
+        final engine = _engine;
+        if (engine == null) return false;
+        return engine.useLineBomb(row: row, col: col);
+      });
+
+  Future<BoosterUseResult> _useBooster(
+      BoosterType type, bool Function() apply) async {
+    final engine = _engine;
+    if (engine == null) return BoosterUseResult.noBooster;
+    final inv = ref.read(boosterInventoryProvider.notifier);
+    if ((ref.read(boosterInventoryProvider)[type] ?? 0) <= 0) {
+      return BoosterUseResult.noBooster;
+    }
+    if (!apply()) return BoosterUseResult.invalidTarget;
+    await inv.consume(type);
+    _publish(lastPlacement: null);
+    return BoosterUseResult.success;
+  }
+
   void _publish({required PlacementResult? lastPlacement}) {
     final engine = _engine!;
     state = GameViewState(