troubleshooting: Windows off the screen

[Some tips from Sietse](https://discuss.bluerobotics.com/t/cockpit-display/23519/4):

> It usually happens after Cockpit has been opened on an external monitor. After disconnecting the monitor, Windows sometimes still thinks Cockpit should open on that now-nonexistent display. In your video, the brief white flashing animation appears to show Cockpit opening on this “virtual” external screen.
>
> A workaround that consistently works for me is:
>
> Open Cockpit, even though its window is not visible.
>
> Open any other application.
>
> Activate Windows’ split-screen function by dragging the visible application to the side or corner of the display.
>
> aWindows should then show Cockpit as one of the available applications for the other half of the screen.
>
> Select Cockpit.
>
> Once Cockpit is visible again, close the second application and maximise Cockpit.
>
> Cockpit should then return to the laptop’s main display and can be used normally again.

Start by locating the appropriate troubleshooting page in the Cockpit-docs repository and review the linked discussion for context. Document the Windows off-screen workaround from the issue, including the steps for restoring Cockpit to the laptop display and the external-monitor cause.

Written by the indexing model from the issue text.