Rewrite and simplify Inventory Menu, various fixes for item effects

Zennysoft.Game.Ma/src/items/Inventory.cs

@@ -19,6 +19,7 @@ public partial class Inventory : Node, IInventory
   private const int _maxInventorySize = 20;
 
   public event Action<string> BroadcastMessage;
+  public event Action InventoryChanged;
 
   public Inventory()
   {
@@ -32,10 +33,7 @@ public partial class Inventory : Node, IInventory
   {
     var isAdded = TryAdd(item);
     if (isAdded)
-    {
       BroadcastMessage?.Invoke($"{item.ItemName} picked up.");
-      item.QueueFree();
-    }
     else
       BroadcastMessage?.Invoke($"Could not pick up {item.ItemName}.");
 
@@ -48,6 +46,7 @@ public partial class Inventory : Node, IInventory
       return false;
 
     Items.Add(inventoryItem);
+    InventoryChanged?.Invoke();
     return true;
   }
 
@@ -57,11 +56,15 @@ public partial class Inventory : Node, IInventory
       return false;
 
     Items.Insert(index, inventoryItem);
+    InventoryChanged?.Invoke();
     return true;
   }
 
-  public void Remove(InventoryItem inventoryItem) => Items.Remove(inventoryItem);
-
+  public void Remove(InventoryItem inventoryItem)
+  {
+    Items.Remove(inventoryItem);
+    InventoryChanged?.Invoke();
+  }
 
   public void Sort(EquipableItem currentWeapon, EquipableItem currentArmor, EquipableItem currentAccessory)
   {