Add File -> Minimize to tray toggle (default on)

Adds a checkable MenuItem so the user can opt out of the hide-to-tray
behavior. Persisted per-user to %APPDATA%\WebhookServer\gui.json so the
choice survives restarts.

When ticked (default): X / Alt+F4 / minimize hide to tray, GUI process
keeps running, tray icon persists.

When unticked: X actually closes the app, minimize is a regular
Windows minimize.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/WebhookServer.Gui/MainWindow.xaml

@@ -31,6 +31,11 @@
                 <MenuItem Header="_Export config…" Command="{Binding ExportConfigCommand}"/>
                 <MenuItem Header="Config _Checkpoints…" Command="{Binding ShowConfigCheckpointsCommand}"/>
                 <Separator/>
+                <MenuItem Header="_Minimize to tray"
+                          IsCheckable="True"
+                          IsChecked="{Binding MinimizeToTrayEnabled, Mode=TwoWay}"
+                          ToolTip="When ticked, closing or minimizing the window hides it to the tray and keeps the GUI process alive. Untick to make the X button quit the app."/>
+                <Separator/>
                 <MenuItem Header="E_xit" Command="{Binding ExitCommand}"/>
             </MenuItem>
             <MenuItem Header="_Server">

src/WebhookServer.Gui/MainWindow.xaml.cs

@@ -38,7 +38,7 @@ public partial class MainWindow : Window
 
     private void OnClosing(object? sender, CancelEventArgs e)
     {
-        if (ExitForReal)
+        if (ExitForReal || !_vm.MinimizeToTrayEnabled)
         {
             _tray.Dispose();
             return;
@@ -58,9 +58,10 @@ public partial class MainWindow : Window
 
     private void OnStateChanged(object? sender, EventArgs e)
     {
-        // Minimize-to-tray: hide the window when the user minimizes; restoring is
+        // Minimize-to-tray: hide the window when the user minimizes IF they've
-        // via the tray icon's double-click or context menu.
+        // opted in via File -> Minimize to tray. Otherwise behave like a normal
-        if (WindowState == WindowState.Minimized)
+        // Windows minimize.
+        if (WindowState == WindowState.Minimized && _vm.MinimizeToTrayEnabled)
         {
             Hide();
             ShowInTaskbar = false;

src/WebhookServer.Gui/Services/GuiSettings.cs

@@ -0,0 +1,50 @@
+using System.IO;
+using System.Text.Json;
+
+namespace WebhookServer.Gui.Services;
+
+/// <summary>
+/// Per-user GUI preferences that don't belong in the service-side ServerConfig.
+/// Persisted to %APPDATA%\WebhookServer\gui.json. Best-effort: failures to read
+/// or write fall back silently to defaults.
+/// </summary>
+public sealed class GuiSettings
+{
+    /// <summary>
+    /// When true, the X / Alt+F4 / minimize buttons hide the window to the tray
+    /// and keep the GUI process alive. When false, X exits the app and minimize
+    /// behaves like a normal Windows minimize.
+    /// </summary>
+    public bool MinimizeToTrayEnabled { get; set; } = true;
+
+    private static string FilePath => Path.Combine(
+        Environment.GetFolderPath(Environment.SpecialFolder.ApplicationData),
+        "WebhookServer",
+        "gui.json");
+
+    public static GuiSettings Load()
+    {
+        try
+        {
+            if (File.Exists(FilePath))
+            {
+                var json = File.ReadAllText(FilePath);
+                if (!string.IsNullOrWhiteSpace(json))
+                    return JsonSerializer.Deserialize<GuiSettings>(json) ?? new GuiSettings();
+            }
+        }
+        catch { /* fall through to defaults */ }
+        return new GuiSettings();
+    }
+
+    public void Save()
+    {
+        try
+        {
+            var dir = Path.GetDirectoryName(FilePath);
+            if (!string.IsNullOrEmpty(dir)) Directory.CreateDirectory(dir);
+            File.WriteAllText(FilePath, JsonSerializer.Serialize(this, new JsonSerializerOptions { WriteIndented = true }));
+        }
+        catch { /* best effort */ }
+    }
+}

src/WebhookServer.Gui/ViewModels/MainViewModel.cs

@@ -29,17 +29,28 @@ public sealed partial class MainViewModel : ObservableObject
     [ObservableProperty] private ServerConfig _serverConfig = new();
     [ObservableProperty] private string _httpBaseUrl = "http://localhost:8080";
     [ObservableProperty] private string? _httpsBaseUrl;
+    [ObservableProperty] private bool _minimizeToTrayEnabled;
 
     private readonly DispatcherTimer _logTimer;
+    private readonly GuiSettings _settings;
 
     public MainViewModel(AdminPipeClient client)
     {
         _client = client;
+        _settings = GuiSettings.Load();
+        _minimizeToTrayEnabled = _settings.MinimizeToTrayEnabled;
+
         _logTimer = new DispatcherTimer(DispatcherPriority.Background) { Interval = TimeSpan.FromSeconds(3) };
         _logTimer.Tick += async (_, _) => await RefreshLogTailAsync();
         _logTimer.Start();
     }
 
+    partial void OnMinimizeToTrayEnabledChanged(bool value)
+    {
+        _settings.MinimizeToTrayEnabled = value;
+        _settings.Save();
+    }
+
     [RelayCommand]
     private async Task RefreshAsync()
     {