Redesign and reimplement inventory menu

Add jewels but no implementation yet (needed redesign of inventory menu to function correctly)

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

@@ -6,6 +6,7 @@ using System;
 using System.Collections.Generic;
 using System.Linq;
 using Zennysoft.Game.Abstractions;
+using Zennysoft.Game.Implementation;
 using Zennysoft.Ma.Adapter;
 
 namespace Zennysoft.Game.Ma;
@@ -96,9 +97,10 @@ public partial class Inventory : Node, IInventory
     foreach (var itemStack in itemsToStack)
     {
       var firstItem = itemStack.First();
-      firstItem.SetCount(itemStack.Count());
+      firstItem.SetCount(itemStack.Sum(x => x.Count.Value));
       var itemsToRemove = itemStack.Except([firstItem]).Cast<InventoryItem>();
-      Items = [.. Items.Except(itemsToRemove)];
+      foreach (var item in itemsToRemove)
+        Remove(item);
     }
 
     return !Items.SequenceEqual(initialList);