Add event publishing for inventory and combat interactions

GameCore/Inventory/InventorySystem.cs

@@ -21,6 +21,10 @@ public class InventorySystem : ISystem
     private void OnAddItem(AddItemToInventoryEvent e)
     {
         var inventory = _world.GetComponent<InventoryComponent>(e.Target);
-        inventory?.AddItem(e.Item);
+        if (inventory == null) return;
+        inventory.AddItem(e.Item);
+
+        var newQuantity = inventory.GetItemCount(e.Item.ItemId);
+        _world.PublishEvent(new InventoryItemChangedEvent(e.Target, e.Item.ItemId, newQuantity));
     }
 }

GameCore/Inventory/ItemAcquisitionSystem.cs

@@ -27,6 +27,7 @@ public class ItemAcquisitionSystem : ISystem
 
         if (pickupComponent.IsInstantUse)
         {
+            _world.PublishEvent(new InstantItemUsedEvent(e.Picker, e.ItemId));
             var context = new EffectContext
             {
                 World = _world,