feat(rig): the LCXL3 driver joins the supervised rig — one inventory, one painter

The night's lesson, converged: the driver only ran when a session remembered to
start it, then the session's background task got OOM-reaped and the surface sat
untranslated with every check green.

- tools/lcxl3-driver.service: repo-owned unit like its siblings; retry-forever
  hotplug posture; Conflicts=lcxl-leds-watch so exactly one painter owns the
  board; follow-mode (no --track) so paint tracks the loaded file.
- rig_units.py: lcxl3-driver + perf-tray rows (THE list is complete again),
  new 'manual' boot policy so --ensure can never start the v2 painter into a
  Conflicts= kill; --list --boot filter for shell consumers.
- parvagues-gear: moved into the repo; derives its sets from rig_units --list
  instead of being the fourth hardcoded copy; autostart-on now defers to
  --ensure (it used to enable parvagues-sc at login against policy).
- gig-up.sh leds(): detects the plugged surface generation and hands the LCXL3
  to the driver unit; v2 path invoked via python3 (exec-bit-proof).

tools/lcxl3-driver.service

+[Unit]
+Description=LCXL3 translation driver (v3 DAW protocol -> v2 corpus CCs + paint + OLED)
+Documentation=file:///home/pln/Work/Sound/Tidal/tools/lcxl3-driver.py
+# Born 2026-09-05, the night the LCXL3 sat untranslated while every check was
+# green: the driver only ran when a session remembered to start it, and the
+# session that started it got reaped. Faders -> Ardour gains live on this path;
+# without it the surface is a very nice-looking brick.
+#
+# The surface is hot-pluggable and the USB-C hub drops it. Same posture as
+# lcxl-leds-watch: retry forever, bind within RestartSec of a replug.
+# StartLimitIntervalSec=0 must live HERE in [Unit] — in [Service] systemd
+# silently ignores it and the unit falls into `failed` after 5 restarts with
+# the surface deaf for the rest of the session.
+StartLimitIntervalSec=0
+# ONE painter owns the board. The v2 watcher (lcxl-leds-watch) speaks the old
+# device's SysEx and misreads the LCXL3's silence as a USB OUT stall. With
+# Conflicts=, starting either painter stops the other — plugging a generation
+# of surface picks its painter, and two writers can never fight over the LEDs.
+Conflicts=lcxl-leds-watch.service
+
+[Service]
+Type=simple
+WorkingDirectory=/home/pln/Work/Sound/Tidal
+# Python block-buffers stdout under systemd; without this the journal shows
+# nothing and the driver's diagnostics die unflushed in a 4 KB buffer.
+Environment=PYTHONUNBUFFERED=1
+# No --track: the driver follows ~/.cache/parvagues/current-track (<1 s tick),
+# so paint and OLED labels track what is actually loaded instead of a name
+# frozen at unit start. --relative was settled with PLN 2026-08-29 (the driver
+# integrates encoder deltas and owns the values — pot-pickup cannot exist).
+ExecStart=/usr/bin/python3 /home/pln/Work/Sound/Tidal/tools/lcxl3-driver.py --relative --paint
+
+Restart=always
+RestartSec=5
+
+# Deliberately NOT niced down, unlike the LED watcher: this unit is the
+# surface's nervous system (every fader move to Ardour crosses it), and its
+# work is a few byte translations per event — starving it adds latency to
+# the hands, not safety to the audio.
+
+[Install]
+WantedBy=default.target

tools/parvagues-gear

+#!/usr/bin/env bash
+# parvagues-gear — pause/resume the whole ParVagues rig as one unit.
+#
+# Why: the gear set autostarts at login and runs forever — sclang+scsynth burn
+# ~2.6W idle, and midi-autoconnect / tidal-ardour-autoroute poll every 2s.
+# On battery (esp. this worn pack) that's real minutes. There was no "off".
+#
+# THE UNIT LIST IS NOT AUTHORED HERE. tools/rig_units.py owns it (the
+# "list lived in three places" lesson); this script derives its sets from
+# `rig_units.py --list`. Adding a unit to the rig = one row there, and gear
+# pauses/resumes it with no edit here. "manual"-policy units (the v2 LED
+# watcher) are paused if running but never resumed — resuming one would
+# Conflicts=-kill the LCXL3 driver.
+#
+# ORDER MATTERS: parvagues-sc-watchdog is Restart=always and exists to restart
+# SC when scsynth dies. Stop the watchdog FIRST or it resurrects SC; on resume,
+# start SC FIRST so the watchdog doesn't race it.
+set -euo pipefail
+
+DIR="$(cd "$(dirname "$(readlink -f "${BASH_SOURCE[0]}")")/.." && pwd)"
+
+WATCHDOG=parvagues-sc-watchdog
+SC=parvagues-sc
+REST=()          # startable units minus SC + watchdog (order handled above)
+MANUAL=()        # never resumed; paused only if running
+while IFS= read -r u; do
+  [[ $u == "$SC" || $u == "$WATCHDOG" ]] && continue
+  REST+=("$u")
+done < <(python3 "$DIR/tools/rig_units.py" --list --boot auto)
+while IFS= read -r u; do MANUAL+=("$u"); done \
+  < <(python3 "$DIR/tools/rig_units.py" --list --boot manual)
+ALL=("$WATCHDOG" "$SC" "${REST[@]}" "${MANUAL[@]}")
+
+pwr() {
+  local c v
+  c=$(cat /sys/class/power_supply/BAT0/current_now 2>/dev/null) || return 0
+  v=$(cat /sys/class/power_supply/BAT0/voltage_now)
+  awk -v c="$c" -v v="$v" 'BEGIN{printf "%.1fW", c/1e6*v/1e6}'
+  echo " · battery $(cat /sys/class/power_supply/BAT0/capacity)%"
+}
+
+case "${1:-status}" in
+  pause)
+    systemctl --user stop "$WATCHDOG"          # before SC, or it restarts it
+    systemctl --user stop "$SC" "${REST[@]}" "${MANUAL[@]}"
+    echo "gear paused · $(pwr)"
+    ;;
+  resume)
+    systemctl --user start "$SC"               # before watchdog, avoid the race
+    systemctl --user start "$WATCHDOG" "${REST[@]}"
+    echo "gear resumed · $(pwr)"
+    ;;
+  status)
+    for u in "${ALL[@]}"; do
+      printf '  %-28s %s\n' "$u" "$(systemctl --user is-active "$u")"
+    done
+    echo "  $(pwr)"
+    ;;
+  autostart-off) systemctl --user disable "${ALL[@]}" ;;
+  # enable-per-policy lives in ONE place; this also starts what should run.
+  # (The old inline `enable ALL` was enabling parvagues-sc at login, against
+  # its own on-demand policy — a login must not start SuperDirt.)
+  autostart-on)  python3 "$DIR/tools/rig_units.py" --ensure --apply ;;
+  *) echo "usage: parvagues-gear {pause|resume|status|autostart-off|autostart-on}" >&2; exit 2 ;;
+esac