Enable IBus on OSK interaction conditions
gnome-shell changed OSK focus tracking to using input from IBus, this generally works better than the previous focus tracking based on a11y (wider support, eg. through XIM. Also way less CPU overhead) and brings things closer between wayland and X11 in gnome-shell.
However, it was quite an oversight on my side that gsd-keyboard may optionally disable ibus if no input sources require it... It would be nice to have g-s-d additionally enable IBus on OSK conditions.