Polyseat 0.31.3

Big Picture is built at session start, not when somebody asks for it. A
Steam that is running is not a Big Picture that is ready: with -silent there
is no window at all until the first request, and building it is a few seconds
with the player already watching. That was the last of the wait the autostart
was supposed to remove, and it was reported as exactly that - "Steam is open
already, so why does this take a moment".

So polyseat-steam now ends with Big Picture open, at session start and every
other time it runs. Picking Steam Big Picture in Moonlight is then a workspace
switch and a raise. Verified after a session restart: gamescope up, Steam up and
the window already titled Big-Picture-Modus, with nobody having asked.

It costs memory, and the number is known: 1316 MB summed PSS with Big Picture
open against 732 MB without, measured in this seat. On a machine with 32 GB that
is a trade worth making for a seat whose purpose is to be picked up and used.

Seats have to be provisioned again, generation 53. An application list that
still says polyseat-steam bigpicture keeps working in the meantime; the
argument is accepted and ignored.