Refactor weapon acquisition system to use named constant for no weapon equipped

GameCore/Combat/WeaponAcquisitionSystem.cs

@@ -7,6 +7,7 @@ namespace GameCore.Combat;
 
 public class WeaponAcquisitionSystem : ISystem
 {
+    private const int NoWeaponEquipped = -1;
     private const string WeaponItemPrefix = "weapon_";
     private readonly World _world;
 
@@ -30,7 +31,7 @@ public class WeaponAcquisitionSystem : ISystem
         if (!equipment.EquippableWeaponItemIds.Contains(e.Item.ItemId))
             equipment.EquippableWeaponItemIds.Add(e.Item.ItemId);
 
-        if (equipment.CurrentWeaponIndex == -1)
+        if (equipment.CurrentWeaponIndex == NoWeaponEquipped)
         {
             equipment.CurrentWeaponIndex = equipment.EquippableWeaponItemIds.Count - 1;
             _world.PublishEvent(new EquipWeaponEvent(e.Target, e.Item.ItemId));

GameCore/Player/EquipmentComponent.cs

@@ -4,6 +4,7 @@ namespace GameCore.Player;
 
 public class EquipmentComponent : IComponent
 {
+    private const int NoWeaponIndex = -1;
     public List<string> EquippableWeaponItemIds { get; set; } = [];
-    public int CurrentWeaponIndex { get; set; } = -1; // -1 indicates no weapon equipped
+    public int CurrentWeaponIndex { get; set; } = NoWeaponIndex;
 }