The GUI launcher started SuperDirt, Ardour and Pulsar as raw processes and
never touched the systemd --user layer, so a tray that exits 0 when the shell
takes its host away (perf-tray, Sep 14) or a user-closed MIDI lens (exit 78)
stayed dead: the only convergers were tools/gig-up.sh --converge, rig-doctor
and the Bridge watcher, and the Bridge was dead too. Three days of launches
"worked" with no tray and no lens.

ensure() now refuses to start a unit whose proof process already runs outside
it — which is what makes it safe for the launcher to call --ensure --apply
after scsynth is up instead of spawning a second SuperDirt through
parvagues-sc.service. --status agrees, so a launcher-started SuperDirt is no
longer a false problem row. gig-up.sh converges right after the ready-wait,
and honours the midiviz close-latch (the tray's MIDI Monitor button is the
way back within a session).