fix: 补 _knownMunitions 字段声明

src/Unity/Assets/Scripts/Managers/SimulationRunner.cs

@@ -28,6 +28,7 @@ namespace CounterDrone.Unity
 
         private readonly Dictionary<string, GameObject> _entityVisuals = new();
         private readonly Dictionary<string, GameObject> _clouds = new();
+        private readonly HashSet<string> _knownMunitions = new();
 
         public SimulationEngine Engine => _engine;