Make the idle-lock watcher survive a clean exit, and outlive a session restart

`swayidle-lock.service` was `enabled`, in `default.target.wants/`, and **dead for eight days**:

    Active: inactive (dead) since Mon 2026-10-12 16:22:23 PDT; 1 week 1 day ago
    Duration: 2d 21h 57min   Main PID: 3181 (code=exited, status=0/SUCCESS)
    Result=success  NRestarts=0

`Restart=on-failure` cannot see a clean exit, and `swayidle -w` exits 0 on SIGTERM. So the
watcher that owns both the 5-minute idle lock and the `before-sleep` lock stopped existing, and
nothing on the box noticed. The consequence is not cosmetic: with `HandleLidSwitch=suspend` and
`HandleLidSwitchExternalPower=""` (which falls back to it), **closing the lid suspended the
machine unlocked**, because the hook that locks on sleep lived inside the unit that had died. No
alternative was running: `pgrep -c -u blankpad 'swayidle|swaylock|hyprlock|gtklock'` = 0, and
neither `autostart.kdl` launches a locker.

Three settings, each with a job:

- `Restart=always` — a supervisor must not assume it can only die badly.
- `StartLimitIntervalSec=0` — with `always`, a fast loop must never wedge the unit into `failed`;
  a lock that keeps trying beats a lock that stopped trying.
- `PartOf=graphical-session.target` — it is wanted by `default.target`, so a session restart
  brought the target back without it; now the watcher is restarted with the session.

What triggered the 16:22 exit is **unattributed**: the user journal has no entries in that window,
so all that can be said is that swayidle exited with status 0 — precisely what the old policy was
blind to. The fix does not depend on knowing the trigger, which is the point.

Verification is behavioural, per the law recorded with it: start the unit, `kill -TERM` the main
PID, and watch `NRestarts` increment with a new `MainPID` — the October event, survived. Not
performed here: starting it arms a 5-minute idle lock on a machine that has gone a week without
one, and that is Frank's call. `systemd-analyze --user verify` clean, `bats tests/` 71/71,
`kb-lint.sh omp-docs` 0, `kb-coverage.py` 0.

Refs #47

omp-docs/tools/dotfiles-deploy.md

@@ -205,3 +205,33 @@ it in the other. Re-dump on the box whose settings are canonical (`dconf dump /
 dotfiles/dconf/dump.txt`), then delete the state sections before committing — the census's
 *Never track: app state* class applies inside a tracked file, not just to whole directories.
 Refs #44.
+
+## Law: a watcher must restart on a clean exit too
+
+`swayidle-lock.service` was `enabled`, present in `default.target.wants/`, and **dead for eight
+days**: `Result=success`, `NRestarts=0`, gone since 2026-10-12 16:22 after 2d 21h of uptime.
+`Restart=on-failure` cannot see a clean exit, and `swayidle -w` exits 0 on SIGTERM — so the
+watcher that owns the 5-minute idle lock *and* the `before-sleep` lock quietly stopped existing,
+and nothing noticed. With it dead and logind at `HandleLidSwitch=suspend`, closing the lid
+suspended the machine **unlocked**: the lock hook lived inside the thing that had died. No
+alternative existed — `pgrep -c -u blankpad 'swayidle|swaylock|hyprlock|gtklock'` = 0, and neither
+`autostart.kdl` launches a locker.
+
+Three settings, each with a job: `Restart=always`, because a supervisor must not assume it can
+only die badly; `StartLimitIntervalSec=0`, because a fast loop must never wedge it into `failed` —
+a lock that keeps trying beats one that stopped trying; and `PartOf=graphical-session.target`,
+because the unit is wanted by `default.target`, so the session coming back did not bring *it*
+back.
+
+Verify by behaviour rather than by reading the file — the point is surviving the event that killed
+it in October:
+
+```bash
+systemctl --user start swayidle-lock.service
+kill -TERM "$(systemctl --user show swayidle-lock.service -p MainPID --value)"
+sleep 8 && systemctl --user show swayidle-lock.service -p NRestarts -p MainPID -p ActiveState
+```
+
+The general shape: `deploy.sh` only ever *enables*. Nothing on any box re-checks that a unit the
+system depends on is still running, so a security posture can lapse silently and stay lapsed for a
+week. A liveness check for this tier belongs in the heartbeat, not in a human's memory. Refs #47.