This will be completely non-functional for a long time.
The idea is to transfer the interactions and convergent UI design
from the ui-design.md text file to a working demo, and only when
(or if) it works, try to merge it with the codebase of Skanpage
to get something useful out of it. Skanpage won't stand still
in the meantime, the best way to avoid continuous merge pain is
to stick to Marascan's unique elements and defer the rest as long
as possible.

As a start, this is taking a shot at the back-and-forth between
the Scan Options and Page Grid views.

I had a hard time placing the Scan action on the desktop toolbar
because I wanted it as far left as possible, but Kirigami
right-aligns all primary actions and with Scan Options visible,
it ends up in an awkward spot in the middle. As a workaround for
the time being, I put it into the leftmost visible Page as main
Primary Action and make it invisible in the ones further right.

Perhaps Kirigami will one day allow me to add more "global actions"
toolbar buttons left-aligned next to the hamburger menu.