added a ban on running a second instance of the application.

CursorLang/App.xaml.cs

@@ -13,11 +13,23 @@ namespace CursorLang;
 public partial class App : Application
 {
     private ServiceProvider? _services;
+    private SingleInstanceGate? _instanceGate;
 
     protected override void OnStartup(StartupEventArgs e)
     {
         base.OnStartup(e);
 
+        var gate = new SingleInstanceGate();
+        if (!gate.TryAcquire())
+        {
+            gate.Dispose();
+            Shutdown();
+            return;
+        }
+
+        _instanceGate = gate;
+        _instanceGate.ActivationRequested += OnActivationRequested;
+
         var services = new ServiceCollection();
         ConfigureServices(services);
         _services = services.BuildServiceProvider();
@@ -34,9 +46,31 @@ public partial class App : Application
     protected override void OnExit(ExitEventArgs e)
     {
         _services?.Dispose();
+
+        if (_instanceGate is not null)
+        {
+            _instanceGate.ActivationRequested -= OnActivationRequested;
+            _instanceGate.Dispose();
+        }
+
         base.OnExit(e);
     }
 
+    private void OnActivationRequested(object? sender, EventArgs e)
+    {
+        if (MainWindow is not { IsVisible: true })
+        {
+            return;
+        }
+
+        if (MainWindow.WindowState == WindowState.Minimized)
+        {
+            MainWindow.WindowState = WindowState.Normal;
+        }
+
+        MainWindow.Activate();
+    }
+
     private static void ConfigureServices(IServiceCollection services)
     {
         services.AddSingleton(new KeyboardLayoutOptions());