enzo/kusanagi: idle suspend via swayidle

Bare niri has no power daemon watching for inactivity, so neither box
slept on its own. Add a user swayidle service bound to
graphical-session.target that fires after 15 min of no input:

  - enzo: suspend-then-hibernate (matches the existing lid-switch policy)
  - kusanagi: plain suspend-to-RAM, plus Wake-on-LAN on enp9s0 so it can
    be woken remotely while the Kavita/Immich/Ollama/NFS servers sleep

Assisted-by: Claude:claude-opus-4-8

1 files changed, 17 insertions, 0 deletions

diff --git a/machines/enzo/default.nix b/machines/enzo/default.nix
index bcb92cb..7247a3e 100644
--- a/machines/enzo/default.nix
+++ b/machines/enzo/default.nix
@@ -77,6 +77,23 @@
   services.logind.settings.Login.HandleLidSwitch = "suspend-then-hibernate";
   systemd.sleep.settings.Sleep.HibernateDelaySec = "60min";
 
+  # Idle trigger. Bare niri has no power daemon watching for inactivity, so with
+  # the lid open the box never sleeps on its own. swayidle (a Wayland idle
+  # client) fires the same suspend-then-hibernate after 15 min of no input. niri
+  # binds it to graphical-session.target and exports WAYLAND_DISPLAY to the user
+  # manager, so this Just Works in the session. `-w` waits for the resume to
+  # finish before re-arming the timer.
+  systemd.user.services.swayidle = {
+    description = "Suspend-then-hibernate after idle";
+    wantedBy = [ "graphical-session.target" ];
+    partOf = [ "graphical-session.target" ];
+    after = [ "graphical-session.target" ];
+    serviceConfig = {
+      ExecStart = "${pkgs.swayidle}/bin/swayidle -w timeout 900 'systemctl suspend-then-hibernate'";
+      Restart = "on-failure";
+    };
+  };
+
   # btrfs + SSD upkeep.
   services.btrfs.autoScrub.enable = true;
   services.fstrim.enable = true;