NotifyIcon.ParentHandle unused?

Describe the bug

I wanted to set the parent handle directly instead of using the automatic mechanism which tries to get the HwndSource from the main window, which might not be available yet due to the window being hidden at startup.

It seems that the property ParentHandle isn't used at all, neither by the NotifyIcon class nor the InternalNotifyIconManager.

To Reproduce

protected override void OnStartup(StartupEventArgs e)
{
    base.OnStartup(e);

    var mainWindow = new MainWindow();
    MainWindow = mainWindow;

    var helper = new WindowInteropHelper(mainWindow);

    var trayIcon = new NotifyIcon()
    {
        Icon = new BitmapImage(new Uri("pack://application:,,,/Resources/icon.ico")),
        ContextMenu = new ContextMenu()
        {
            Items =
            {
                new MenuItem()
                {
                    Header = "Exit",
                }
            }
        },
        ParentHandle = helper.EnsureHandle(),
        TooltipText = "Test",
    };

    trayIcon.Register();
    _trayIcon = trayIcon;
}

Expected behavior

The InternalNotifyIconManager should use the ParentHandle instead of trying to find the handle of the main window.

Screenshots

No response

OS version

Win 11 24H2

.NET version

.NET Framework 4.7.2

WPF-UI NuGet version

4.0.0-rc.2

Additional context

No response

Start by inspecting the NotifyIcon and InternalNotifyIconManager classes to trace how the parent window handle is selected during registration. Verify whether ParentHandle is ignored, then make the manager use the explicitly assigned handle and confirm that registration works when the main window is hidden at startup.