Display fix for MacOS x86

QemuVmManager.Core/QemuCommandBuilder.cs

@@ -1,5 +1,6 @@
 using QemuVmManager.Models;
 using System.Diagnostics;
+using System.Runtime.InteropServices;
 
 namespace QemuVmManager.Core;
 
@@ -230,7 +231,19 @@ public class QemuCommandBuilder
         var display = _config.Display;
         
         _arguments.Add("-display");
-        _arguments.Add(display.Type);
+        
+        // Use appropriate display backend based on OS
+        string displayType = display.Type;
+        if (OperatingSystem.IsMacOS())
+        {
+            // On macOS, GTK is not available, use cocoa instead
+            if (displayType == "gtk")
+            {
+                displayType = "cocoa";
+            }
+        }
+        
+        _arguments.Add(displayType);
         
         _arguments.Add("-vga");
         _arguments.Add(display.Vga);