Resolve "Overview: Can't use the keyboard to choose the Dash when mouse is on a window"
Since commit 1939e22c, we move the keyboard focus with the hover highlight. However while this makes sense when interacting with the window picker, it interferes with keyboard navigation of other components like dash or top bar. Address this by only moving the focus when the previous focus was already inside the window picker or unset.
Closes #50 (closed)