feat(tray): minimize sends Settings to tray; rename Exit -> Quit

The app already used ShutdownMode=OnExplicitShutdown, so closing the
Settings window via the X already kept the app alive in the tray.
But the minimize ('-') button still went to the taskbar, which is the
wrong UX for a tray app. Two small changes:

* SettingsWindow.OnStateChanged: when WindowState becomes Minimized,
  close the window instead. The taskbar entry disappears and the app
  stays in the tray, identical to clicking X. Reopen via tray icon
  double-click or the tray's Settings menu item.

* TrayIconHost: rename 'Exit' to 'Quit' to match the user-facing
  vocabulary (and to make it clear that this is the only path that
  fully terminates the process).

Behavior summary after this change:
* X on Settings    -> window closes, app stays in tray
* '-' on Settings  -> window closes, app stays in tray (was: taskbar)
* Save & close     -> persists, window closes, app stays in tray
* Cancel           -> discards, window closes, app stays in tray
* Tray > Quit      -> ExitApp: dispose tray + monitor + Shutdown()

Author: carterscode

src/GamerGuardian/Tray/TrayIconHost.cs

@@ -23,7 +23,10 @@ public TrayIconHost()
         _pauseItem = new ToolStripMenuItem("Pause monitoring", null, (_, _) => PauseToggleRequested?.Invoke());
         menu.Items.Add(_pauseItem);
         menu.Items.Add(new ToolStripSeparator());
-        menu.Items.Add("Exit", null, (_, _) => ExitRequested?.Invoke());
+        // 'Quit' is the only path that fully terminates the process. Closing or
+        // minimizing the Settings window goes to the tray (App.xaml has
+        // ShutdownMode=OnExplicitShutdown).
+        menu.Items.Add("Quit", null, (_, _) => ExitRequested?.Invoke());
 
         _icon = new NotifyIcon
         {

src/GamerGuardian/UI/SettingsWindow.xaml.cs

@@ -619,6 +619,22 @@ private void PersistFormToConfig()
 
     private bool _suppressSaveOnClose = false;
 
+    /// <summary>
+    /// Redirects minimize (the '-' button or Win+Down) to a close: the window
+    /// destroys, taskbar entry disappears, app stays in the tray. Reopen via
+    /// double-click on the tray icon or the tray's Settings menu item.
+    /// Without this, minimize would just shrink to a taskbar entry, which is
+    /// the wrong UX for a tray app.
+    /// </summary>
+    protected override void OnStateChanged(EventArgs e)
+    {
+        base.OnStateChanged(e);
+        if (WindowState == WindowState.Minimized)
+        {
+            Close();
+        }
+    }
+
     private void OnWindowClosing(object? sender, CancelEventArgs e)
     {
         if (_suppressSaveOnClose) return;