Refactor ConsumeAmmoCost to use readonly field for ammoId and improve Entity struct equality methods

GameCore/Combat/Effects/ConsumeAmmoCost.cs

@@ -6,20 +6,22 @@ namespace GameCore.Combat.Effects;
 
 public class ConsumeAmmoCost(string ammoId, int amount) : ICostEffect
 {
+    public readonly string AmmoId = ammoId;
+    
     public void Execute(EffectContext context)
     {
         var inventory = context.World.GetComponent<InventoryComponent>(context.Owner);
         if (inventory == null) return;
 
-        inventory.RemoveItem(ammoId, amount);
+        inventory.RemoveItem(AmmoId, amount);
 
-        var newQuantity = inventory.GetItemCount(ammoId);
-        context.World.PublishEvent(new InventoryItemChangedEvent(context.Owner, ammoId, newQuantity));
+        var newQuantity = inventory.GetItemCount(AmmoId);
+        context.World.PublishEvent(new InventoryItemChangedEvent(context.Owner, AmmoId, newQuantity));
     }
 
     public bool CanAfford(EffectContext context)
     {
         var inventory = context.World.GetComponent<InventoryComponent>(context.Owner);
-        return inventory != null && inventory.HasItem(ammoId, amount);
+        return inventory != null && inventory.HasItem(AmmoId, amount);
     }
 }

GameCore/ECS/Entity.cs

@@ -1,3 +1,5 @@
+using System.Diagnostics.CodeAnalysis;
+
 namespace GameCore.ECS;
 
 /// <summary>
@@ -8,4 +10,14 @@ namespace GameCore.ECS;
 public readonly struct Entity(int id)
 {
     public readonly int Id = id;
+
+    public override bool Equals([NotNullWhen(true)] object? obj)
+    {
+        return base.Equals(obj);
+    }
+
+    public override int GetHashCode()
+    {
+        return Id.GetHashCode();
+    }
 }