[i3] Setup brightness control with ddcutil

roles/desktop/x11.nix

@@ -19,8 +19,20 @@ in
           polkit_gnome                    # GNOME polkit authentication agent (more stable with i3)
           picom                           # Compositor for smooth rendering (important for Nvidia)
           networkmanagerapplet            # NetworkManager system tray applet
+          ddcutil                         # DDC/CI monitor control for brightness
         ];
       };
     };
+
+    # Enable DDC/CI support for monitor brightness control
+    boot.kernelModules = [ "i2c-dev" ];
+
+    # Add ddcutil udev rules and user permissions
+    hardware.i2c.enable = true;
+
+    # Install ddcutil system-wide
+    environment.systemPackages = with pkgs; [
+      ddcutil
+    ];
   };
 }