:spawn -d processes are reported as "running" even when they are not

[emanuele6]

Version info:

qutebrowser v3.1.0
Git commit: 
Backend: QtWebEngine 6.6.2, based on Chromium 112.0.5615.213 (from api)
Qt: 6.6.2

Does the bug happen if you start with --temp-basedir?:
Yes

Description
When you spawn a detached process, qutebrowser shows it as pid 0, and says it is running even though it is not.

completion	qute://process/

Since detached processes are not qutebrowser's children, it makes sense that it cannot know their exit status, and that it does not get notified when they terminate, but it would be less confusing if qutebrowser didn't say that their status is "running".

How to reproduce
:spawn -d echo hi

[emanuele6]

There could be a special detached status, but maybe detached processes should just not be shown at all in :process completion; qutebrowser cannot provide any useful information about them except their commandline (and maybe potentially their pid).