feat(nightlight): persistent off via state marker

A manual `off` now drops ~/.local/state/nomarchy/nightlight-off and the
hyprsunset unit refuses to (re)start while it exists
(Unit.ConditionPathExists=!%h/...), so the off survives logout/reboot
until toggled back on. `on`/toggle-on remove the marker before starting
(a failed condition would otherwise no-op the start). Without the marker
behaviour is unchanged: the service stays WantedBy=graphical-session.target
and resumes its schedule at login, so persistence is opt-in via the toggle.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

docs/ROADMAP.md

@@ -459,15 +459,17 @@ how to override it. Items marked ✓ are shipped.
   `nomarchy-menu nightlight` entry (System submenu, self-gated on the unit
   existing) and a self-gating Waybar `custom/nightlight` indicator (moon = on,
   sun = off; in the generated bar and both summer whole-swaps) drive it.
-  The toggle is **session-scoped by design**: `stop` halts the running unit
-  but it's `WantedBy=graphical-session.target`, so the next login auto-starts
-  it and night-light returns to its schedule (off never persists). Remaining
-  (optional): (1) **persistent off** — a state marker
-  (`~/.local/state/nomarchy/nightlight-off`) the unit honours via
-  `ConditionPathExists=!%h/…`, so a manual off survives logout/reboot until
-  toggled back; (2) geo (lat/long) auto sunset/sunrise (would mean wlsunset,
-  which schedules by location). Pending an on-machine check that stopping
-  hyprsunset cleanly restores the gamma.
+  ✓ **Persistent off:** a manual `off` now drops a marker
+  (`~/.local/state/nomarchy/nightlight-off`) and the unit refuses to (re)start
+  while it exists (`Unit.ConditionPathExists=!%h/…`), so an off survives
+  logout/reboot until toggled back on; `on`/toggle-on remove the marker first
+  (a failed condition would otherwise no-op the start). Without the marker the
+  service stays `WantedBy=graphical-session.target` and resumes its schedule at
+  login as before — the session-scoped behaviour is now the *default*, with
+  persistence opt-in via the toggle. Remaining (optional): geo (lat/long) auto
+  sunset/sunrise (would mean wlsunset, which schedules by location). Pending an
+  on-machine check (off persisting across reboot, and that stopping hyprsunset
+  cleanly restores the gamma).
 - **Keyboard layouts (per-device + switching):**
   - ✓ **Per-device declarative layout:** `nomarchy.keyboard.devices`
     (`{ "<hyprctl-device-name>" = { layout; variant; }; }`) generates Hyprland

modules/home/nightlight.nix

@@ -21,6 +21,12 @@ let
   # module hides itself — same pattern as the power-profile indicator.
   nomarchy-nightlight = pkgs.writeShellScriptBin "nomarchy-nightlight" ''
     unit=hyprsunset.service
+    # Persistent-off marker — mirrors the unit's ConditionPathExists below.
+    # Present => night-light stays off across logout/reboot until toggled on.
+    # Path is literal (not XDG_STATE_HOME) so it matches the unit's %h check.
+    marker="$HOME/.local/state/nomarchy/nightlight-off"
+    mark_off() { mkdir -p "$(dirname "$marker")"; : > "$marker"; }
+    mark_on()  { rm -f "$marker"; }
     if ! systemctl --user cat "$unit" >/dev/null 2>&1; then
       [ "''${1:-}" = status ] && exit 0
       notify-send "Night light" "Not enabled — set nomarchy.nightlight.enable."
@@ -33,14 +39,14 @@ let
         else
           printf '{"text":"󰖙","tooltip":"Night light off (click to enable)","class":"off"}\n'
         fi ;;
-      on)  systemctl --user start "$unit" ;;
-      off) systemctl --user stop "$unit" ;;
+      on)  mark_on;  systemctl --user start "$unit" ;;
+      off) mark_off; systemctl --user stop "$unit" ;;
       toggle)
         if systemctl --user is-active --quiet "$unit"; then
-          systemctl --user stop "$unit"
-          notify-send "Night light off" "Screen back to true colours."
+          mark_off; systemctl --user stop "$unit"
+          notify-send "Night light off" "Screen back to true colours (stays off until re-enabled)."
         else
-          systemctl --user start "$unit"
+          mark_on; systemctl --user start "$unit"
           notify-send "Night light on" "Warm filter follows your schedule."
         fi ;;
       *) echo "usage: nomarchy-nightlight [toggle|status|on|off]" >&2; exit 64 ;;
@@ -59,6 +65,13 @@ in
       ];
     };
 
+    # Persistent off: a manual `off` drops ~/.local/state/nomarchy/nightlight-off,
+    # and this Condition makes the unit refuse to (re)start while it exists — so
+    # an off survives logout/reboot. `nomarchy-nightlight on` removes it first
+    # (a failed condition would otherwise no-op the start). %h = $HOME.
+    systemd.user.services.hyprsunset.Unit.ConditionPathExists =
+      lib.mkIf cfg.enable "!%h/.local/state/nomarchy/nightlight-off";
+
     # Always on PATH (it self-gates at runtime), so a static whole-swap Waybar
     # can exec it even when night-light is off without the call failing.
     home.packages = [ nomarchy-nightlight ];