Asobu 0.1.3

Copy the sign-in code from the welcome, automatically and by hand

The device code has to be typed into a page in another window, which is the one
fiddly step in the whole welcome. The Accounts page has copied it for you since
it was written; the welcome, which is where most people will meet the flow for
the first time, made you read eight characters off the screen.

Same behaviour, same wording, same button: copied the moment it appears, with a
button to do it again and a line saying which happened. The clipboard hangs off
the window rather than the view model, so the copying lives in the view and the
view model only hears that it happened.

Both views can watch the same accounts page safely -- only one of them is ever
mounted while a sign-in runs, since the welcome covers the whole window and the
Accounts page is not built until it is navigated to.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>