Ability for Transitioner to navigate (without transitions) when app is not active (in focus).

Is your feature request related to a problem? Please describe.
I would like to be able to have a transition between pages of my application that are triggered in code after a potentially long running task.
If I run my demo application and click on the Next or Back buttons and then activate another window (e.g. Visual Studio) while the background delay is being awaited, when the process completes no Transition occurs.
However, if the demo app remains the active window it transitions as expected.

Describe the solution you'd like
For the page navigation to happen, ideally with transitions if the windows is visible.
If the window is not visible then page navigation should occur, but maybe without any transitions (instant change to control z-order)

Describe alternatives you've considered
Not sure of any other alternatives other than rolling my own Navigation functionality.

Additional context
My simplified demo app can be found in my Izzy-Transitioner-Demo branch of my fork (see: https://github.com/thepinkmile/MaterialDesignInXamlToolkit/tree/Izzy-Transitioner-Demo)

issue に記載された Transitioner の動作から始め、リンクされた Izzy-Transitioner-Demo ブランチを使って再現し、アクティブなウィンドウと非アクティブなウィンドウを比較します。Next/Back によってトリガーされるナビゲーションを追跡し、ウィンドウが非アクティブな状態でナビゲーションが完了することを done と定義します。サポートされている場合は、ウィンドウが表示されているときにトランジションを保持します。