First real end-to-end run of the ordered launcher aborted immediately at
"starting SuperDirt": open_term() carried a vestigial `local cmd="$1"`
(the sclang command is hardcoded inside the function), but the function is
called with no arguments, so `set -u` turned the unused positional into a
fatal 'unbound variable' before sclang ever spawned.

Dropped the dead parameter. Re-ran: SuperDirt boots headless, claims the
LaunchControl XL (aconnect 16:0 -> SuperCollider 128:3) BEFORE Ardour opens,
then Ardour 9.2.0 (Tidal Multi) + Pulsar come up — the whole rig from one
command, no disconnect/reconnect MIDI dance. Task #9 validated live.