X-GNOME-AutoRestart doesn't work for non-client apps

Hi! I'm the new maintainer of gnome-session upstream, and I found a bug that cinnamon-session seems to have inherited since it forked. So I'm forwarding the bug report here

Some apps like the Orca screen reader set X-GNOME-AutoRestart with the expectation that they'll get restarted in the event of a crash or unclean exit. However, the gnome-session codebase you're forked from has a broken implementation of this for plain apps (i.e. apps that aren't "clients" and don't talk to the session manager via dbus or via XSMP). Orca is an app but not a client, and so X-GNOME-AutoRestart simply doesn't work.

The version of gnome-session you've forked from doesn't autorestart apps that set X-GNOME-AutoRestart=true. Which is, to say the least, incorrect. Upstream gnome-session has since gained a check to only skip autorestart on apps that set that setting and are also clients, because clients get autorestarted when they disconnect from the session manager. In other words, cinnamon-session is failing to handle the case where a non-client app requests autorestart to be enabled.

I don't have an installation of Cinnamon to test with, but you can pretty trivially confirm that the bug exists by running pkill -KILL orca or pkill -ABRT orca and observing that the screen reader doesn't get restarted.

See https://gitlab.gnome.org/GNOME/orca/-/issues/622 and https://gitlab.gnome.org/GNOME/orca/-/merge_requests/255 for some more details.

Start by reproducing the issue with pkill -KILL orca or pkill -ABRT orca, then trace how cinnamon-session handles X-GNOME-AutoRestart for plain applications versus session-manager clients. Compare the behavior with the upstream gnome-session change and the linked Orca reports. Done means a non-client application requesting autorestart is restarted after an unclean exit without breaking client handling.