We currently track windows via MetaWorkspace's ::window-added and
::window-removed signals. Those aren't emitted for override-redirect
windows though, as those aren't actually located on any workspace
(see https://gitlab.gnome.org/GNOME/mutter/-/blob/gnome-41/src/core/window.c#L1322).
While that shouldn't be an issue as there's no good reason to look up
the ShellApp of an OR window, extensions can make modifications that
result in OR windows ending up in places that assume that every window
has an associated ShellApp.
We can either
- accept that extensions break stuff (including badly)
- carefully handle app-less windows everywhere
- extend tracking to OR windows
Opt for the last option, as that's the most user-friendly and least
disruptive one.
It's also simpler to track ::window-created and ::unmanaged, as we
don't have to track workspaces or windows moving between workspaces.