feat(nightlight): menu + Waybar on/off toggle

Add a runtime toggle for the scheduled blue-light filter, the remaining
optional item on the night-light roadmap entry.

nomarchy-nightlight (nightlight.nix, always on PATH) starts/stops the
hyprsunset *service* rather than poking its runtime gamma: `systemctl
--user is-active` is the single source of truth, the screen restores to
true colours when stopped, and it lets you force the filter off for
colour-sensitive work (even at night) and back on without touching config.
It self-gates — `status` prints nothing when the unit is absent — so the
indicator hides itself when night-light isn't enabled.

- Menu: `nomarchy-menu nightlight` toggles it; a self-gated row in the
  System submenu (shown only when the hyprsunset unit exists).
- Waybar: a self-gating `custom/nightlight` indicator (moon = on, sun =
  off), in the generated bar and both summer whole-swap themes for parity.

Verified: home generation builds, generated waybar config carries
custom/nightlight, the menu has the dispatcher case + System row, both
scripts pass bash -n, and status self-gates to empty with no unit. Pending
an on-machine check that stopping hyprsunset cleanly restores the gamma.

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

modules/home/nightlight.nix

@@ -5,14 +5,51 @@
 #
 # The hyprsunset HM service module is provided by home-manager; this only
 # configures it. Override anything with plain services.hyprsunset.* options.
-{ config, lib, ... }:
+#
+# nomarchy-nightlight is the menu/Waybar toggle: it starts/stops the hyprsunset
+# *service* (so `systemctl --user is-active` is the single source of truth and
+# the screen restores to true colours when stopped), letting you force the
+# filter off for colour-sensitive work and back on without touching the config.
+{ config, lib, pkgs, ... }:
 
 let
   cfg = config.nomarchy.nightlight;
+
+  # Toggle/status helper, on PATH so the menu and both the generated and
+  # whole-swap Waybars can drive it by name. Self-gates: when the unit doesn't
+  # exist (night-light not enabled) `status` prints nothing, so the Waybar
+  # module hides itself — same pattern as the power-profile indicator.
+  nomarchy-nightlight = pkgs.writeShellScriptBin "nomarchy-nightlight" ''
+    unit=hyprsunset.service
+    if ! systemctl --user cat "$unit" >/dev/null 2>&1; then
+      [ "''${1:-}" = status ] && exit 0
+      notify-send "Night light" "Not enabled — set nomarchy.nightlight.enable."
+      exit 0
+    fi
+    case "''${1:-toggle}" in
+      status)
+        if systemctl --user is-active --quiet "$unit"; then
+          printf '{"text":"󰖔","tooltip":"Night light on — warm on schedule (click to disable)","class":"on"}\n'
+        else
+          printf '{"text":"󰖙","tooltip":"Night light off (click to enable)","class":"off"}\n'
+        fi ;;
+      on)  systemctl --user start "$unit" ;;
+      off) systemctl --user stop "$unit" ;;
+      toggle)
+        if systemctl --user is-active --quiet "$unit"; then
+          systemctl --user stop "$unit"
+          notify-send "Night light off" "Screen back to true colours."
+        else
+          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 ;;
+    esac
+  '';
 in
 {
-  config = lib.mkIf cfg.enable {
-    services.hyprsunset = {
+  config = {
+    services.hyprsunset = lib.mkIf cfg.enable {
       enable = true;
       settings.profile = [
         # Daytime: identity = no colour change.
@@ -21,5 +58,9 @@ in
         { time = cfg.sunset; temperature = cfg.temperature; }
       ];
     };
+
+    # 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 ];
   };
 }

modules/home/rofi.nix

@@ -178,6 +178,14 @@ let
           && notify-send "Do Not Disturb off" "Notifications resumed."
         exit 0 ;;
 
+      nightlight)
+        # Force the scheduled blue-light filter on/off for the session by
+        # starting/stopping hyprsunset (nomarchy-nightlight, from nightlight.nix).
+        # Self-gated in the menu; guard here too in case it's invoked directly.
+        command -v nomarchy-nightlight >/dev/null 2>&1 \
+          && exec nomarchy-nightlight toggle
+        notify-send "Night light" "Not available (nomarchy.nightlight off?)."; exit 0 ;;
+
       snapshot)
         # btrfs-assistant: snapshot browse / diff / restore / rollback over
         # snapper, elevating via polkit. Shipped system-side with
@@ -219,6 +227,8 @@ let
           row "Network"        network-wireless
           row "Bluetooth"      bluetooth
           row "Do Not Disturb" notification-disabled
+          systemctl --user cat hyprsunset.service >/dev/null 2>&1 \
+            && row "Night light" weather-clear-night
           command -v btrfs-assistant >/dev/null 2>&1 && row "Snapshots" timeshift
           if [ -e "''${bats[0]}" ] && command -v powerprofilesctl >/dev/null 2>&1; then
             row "Power profile" preferences-system-power
@@ -229,6 +239,7 @@ let
           *Network*)          exec "$0" network ;;
           *Bluetooth*)        exec "$0" bluetooth ;;
           *"Do Not Disturb"*) exec "$0" dnd ;;
+          *"Night light"*)    exec "$0" nightlight ;;
           *Snapshots*)        exec "$0" snapshot ;;
           *"Power profile"*)  exec "$0" power-profile ;;
           *Back*)             exec "$0" ;;
@@ -256,7 +267,7 @@ let
         esac ;;
 
       *)
-        echo "usage: nomarchy-menu [tools|system|power|power-profile|theme|clipboard|calc|files|emoji|web|network|bluetooth|capture|keybinds|ask|dnd|snapshot]" >&2
+        echo "usage: nomarchy-menu [tools|system|power|power-profile|theme|clipboard|calc|files|emoji|web|network|bluetooth|capture|keybinds|ask|dnd|nightlight|snapshot]" >&2
         exit 64 ;;
     esac
   '';

modules/home/waybar.nix

@@ -77,7 +77,7 @@ let
 
     modules-left = [ "hyprland/workspaces" "hyprland/window" ];
     modules-center = [ "clock" ];
-    modules-right = [ "tray" "pulseaudio" "cpu" "memory" "custom/powerprofile" ]
+    modules-right = [ "tray" "pulseaudio" "cpu" "memory" "custom/powerprofile" "custom/nightlight" ]
       ++ lib.optional showLanguage "hyprland/language"
       ++ [ "battery" "custom/notification" ];
 
@@ -131,6 +131,16 @@ let
       on-click = "nomarchy-powerprofile-cycle";
     };
 
+    # Night-light (hyprsunset) toggle + state. Self-gates: hidden unless
+    # nomarchy.nightlight is enabled (the status helper prints nothing then).
+    # Click starts/stops the schedule; moon = on, sun = off.
+    "custom/nightlight" = {
+      exec = "nomarchy-nightlight status";
+      return-type = "json";
+      interval = 3;
+      on-click = "nomarchy-nightlight toggle";
+    };
+
     # swaync notification bell + Do-Not-Disturb state. `-swb` streams JSON
     # (text/tooltip/class) on every change, so it tracks count and DND with
     # no polling. Left-click toggles the panel; right-click toggles DND.
@@ -202,11 +212,14 @@ let
       font-weight: bold;
     }
 
-    #tray, #pulseaudio, #cpu, #memory, #custom-powerprofile, #language, #battery, #custom-notification {
+    #tray, #pulseaudio, #cpu, #memory, #custom-powerprofile, #custom-nightlight, #language, #battery, #custom-notification {
       color: @subtext;
       padding: 0 10px;
     }
 
+    /* Night-light active → warm tone, matching the filter it represents. */
+    #custom-nightlight.on { color: @warn; }
+
     /* The power-profile speedometer glyph renders small in its em box —
        size it up so it reads at a glance like the other indicators. */
     #custom-powerprofile { font-size: ${toString (t.fonts.size + 3)}pt; }