feat(nightlight): scheduled blue-light filter via hyprsunset

Add nomarchy.nightlight (opt-in): a scheduled colour-temperature shift via
the HM services.hyprsunset module -- warm (.temperature, default 4000K) at
night, identity (no shift) by day, switching at .sunset / .sunrise. Two
time-based hyprsunset profiles, so hyprsunset handles the schedule and the
on-login state. New modules/home/nightlight.nix, imported in the home module.

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

README.md

@@ -190,6 +190,7 @@ examples: **[docs/OVERRIDES.md](docs/OVERRIDES.md)**.
 | `nomarchy.keyboard.variant` | `""` | XKB variant for the session |
 | `nomarchy.keyboard.devices` | `{}` | Per-device layout overrides (Hyprland `device` blocks keyed by `hyprctl devices` name) — e.g. an external keyboard with its own layout/variant |
 | `nomarchy.keyboard.layouts` | `[]` | Extra candidate layouts; when set, a watcher prompts (rofi) for a layout on a newly-connected keyboard and remembers it per-device |
+| `nomarchy.nightlight.enable` | `false` | Scheduled blue-light filter (hyprsunset) — warm at night (`.temperature`, default 4000K) between `.sunset`/`.sunrise`, no shift by day |
 | `nomarchy.hyprland.enable` | `true` | Nomarchy's Hyprland config |
 | `nomarchy.waybar.enable` | `true` | Nomarchy's Waybar |
 | `nomarchy.rofi.enable` | `true` | Themed rofi launcher + `nomarchy-menu` dispatcher |

docs/ROADMAP.md

@@ -289,9 +289,15 @@ how to override it. Items marked ✓ are shipped.
   switching** of the *same* outputs (Hyprland's per-output rules cover the
   common "external connects → arrange" case, not multi-layout toggles), and
   optionally workspace-to-monitor binding.
-- **Night light / blue-light filter:** schedulable colour-temperature shift
+- ✓ **Night light / blue-light filter:** `nomarchy.nightlight` (opt-in) —
-  via `hyprsunset` (Hyprland-native; wlsunset/gammastep are alternatives) —
+  a scheduled colour-temperature shift via `hyprsunset` (Hyprland-native),
-  sunset/sunrise or a fixed schedule, with a menu + Waybar toggle.
+  warm at night, identity (no shift) by day. `modules/home/nightlight.nix`
+  drives the HM `services.hyprsunset` with two time-based profiles
+  (`sunrise` → identity, `sunset` → `temperature`), so hyprsunset handles the
+  schedule and the on-login state. Needs an on-hardware check that hyprsunset
+  applies the active profile at session start. Remaining (optional): a menu +
+  Waybar toggle to force it on/off, and geo (lat/long) auto sunset/sunrise
+  (would mean wlsunset, which schedules by location).
 - **Keyboard layouts (per-device + switching):**
   - ✓ **Per-device declarative layout:** `nomarchy.keyboard.devices`
     (`{ "<hyprctl-device-name>" = { layout; variant; }; }`) generates Hyprland

modules/home/default.nix

@@ -17,6 +17,7 @@
     ./idle.nix      # hyprlock + hypridle, themed from the same JSON
     ./yazi.nix      # flagship TUI file manager, themed + plugins
     ./osd.nix       # swayosd volume/brightness OSD, themed
+    ./nightlight.nix # scheduled blue-light filter (hyprsunset), opt-in
     ./shell.nix     # zsh + starship + bat/eza/zoxide, themed
     ./keys.nix      # gpg-agent (fronts SSH) + pinentry-qt
     ./fastfetch.nix # system info with the themed Nomarchy logo

modules/home/nightlight.nix

@@ -0,0 +1,25 @@
+# Night light — a scheduled blue-light filter via hyprsunset (Hyprland's own
+# gamma/temperature tool). Warm at night, identity (no shift) by day;
+# hyprsunset's time-based `profile` entries handle the schedule and pick the
+# right state on session start. Opt-in via nomarchy.nightlight.enable.
+#
+# The hyprsunset HM service module is provided by home-manager; this only
+# configures it. Override anything with plain services.hyprsunset.* options.
+{ config, lib, ... }:
+
+let
+  cfg = config.nomarchy.nightlight;
+in
+{
+  config = lib.mkIf cfg.enable {
+    services.hyprsunset = {
+      enable = true;
+      settings.profile = [
+        # Daytime: identity = no colour change.
+        { time = cfg.sunrise; identity = true; }
+        # Night: shift to the warm temperature.
+        { time = cfg.sunset; temperature = cfg.temperature; }
+      ];
+    };
+  };
+}

modules/home/options.nix

@@ -157,6 +157,33 @@ in
       '';
     };
 
+    nightlight = {
+      enable = lib.mkEnableOption ''
+        a scheduled blue-light filter (hyprsunset): warm at night, no shift
+        by day. Opt-in; tune the temperature + sunrise/sunset below'';
+
+      temperature = lib.mkOption {
+        type = lib.types.int;
+        default = 4000;
+        example = 3500;
+        description = "Warm colour temperature (K) applied at night — lower is warmer.";
+      };
+
+      sunrise = lib.mkOption {
+        type = lib.types.str;
+        default = "07:00";
+        example = "06:30";
+        description = "Time (HH:MM) the filter turns OFF — daytime, no colour shift.";
+      };
+
+      sunset = lib.mkOption {
+        type = lib.types.str;
+        default = "20:00";
+        example = "21:00";
+        description = "Time (HH:MM) the filter turns ON — warm.";
+      };
+    };
+
     monitors = lib.mkOption {
       type = lib.types.listOf monitorType;
       default = [ ];