_connectPowerWatches() used Gio.DBusProxy.new_for_bus_sync(), which
blocks gnome-shell's single main thread until the system bus replies.
Since gnome-shell is the Wayland compositor, that stalls the entire
screen for however long it takes — and this runs every time live
wallpaper starts, including automatically at login whenever it was
left enabled. Right after login, with upowerd/D-Bus still warming up
alongside everything else, that block can run for many seconds up to
the ~25s GDBus timeout, which matches reports of the whole system
freezing right after the greeter/login. Switched to the async
new_for_bus(), guarded by a generation counter so a stale in-flight
lookup can't clobber state from a later _stop()/_connectPowerWatches().
Claude