fix(session): recover user services after a broken logout teardown

2026-07-18 dev-box incident: on a warm relogin (user manager kept alive
by the tty1 greetd session — no linger involved) the previous logout's
graphical-session.target stop had been rejected as a destructive
transaction (easyeffects held a queued start job), so the target stayed
active across the logout. Its WantedBy services (cliphist, swaync,
xdg-desktop-portal-*, swayosd, …) crash-looped against the dead Wayland
socket into start-limit-hit, and the next login's plain
'start hyprland-session.target' was a no-op — every session service
stayed failed, doctor red, until a reboot.

Session bring-up (HM's systemd.extraCommands, rendered into the first
exec-once) now stops both hyprland-session.target and a possibly-stale
graphical-session.target, clears failed/start-limit state with
reset-failed, then starts fresh. All three commands are no-ops after a
clean logout or cold boot.

Verified V1: home generation built against this tree renders the new
command chain into hyprland.conf line 1 (nix build of
homeConfigurations.bernardo with the nomarchy input overridden).
V3 pending: warm relogin on hardware — queued in HARDWARE-QUEUE with
exact steps; BACKLOG #149 updated with the incident evidence (the
exec-once posture it watches is defending against a real race).

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

agent/BACKLOG.md

@@ -205,6 +205,18 @@ defending against nothing. Do not rip it out on this note alone: it works, and
 the claim needs a real relogin without linger to test (V3 — the same relogin
 that verifies #148's watcher fix would answer it).
 
+**2026-07-18 evidence: the warm relogin is real post-linger.** On the dev
+box the user manager survived a Hyprland logout (the tty1 greetd session
+keeps it alive — no linger involved) and the teardown broke:
+`graphical-session.target`'s stop transaction was rejected as destructive
+(easyeffects had a queued start job), the target stayed active,
+cliphist/swaync/portals/swayosd crash-looped against the dead Wayland
+socket into `start-limit-hit`, and the relogin's plain `start` was a no-op
+— doctor red for the whole session. Session bring-up now stops stale
+targets + `reset-failed` before starting (`hyprland.nix`
+systemd.extraCommands); relogin V3 check queued in HARDWARE-QUEUE. The
+exec-once posture this entry watches is therefore still earning its keep.
+
 ### 120. A netinstall ISO, next to the fat offline one
 
 **Deferred to PROPOSED 2026-07-16 (Bernardo): not now.** Nothing below is