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, 22 insertions, 0 deletions

diff --git a/machines/kusanagi/default.nix b/machines/kusanagi/default.nix
index c39db8e..bab9acd 100644
--- a/machines/kusanagi/default.nix
+++ b/machines/kusanagi/default.nix
@@ -22,6 +22,28 @@
 
   powerManagement.cpuFreqGovernor = "performance";
 
+  # --- Idle suspend + Wake-on-LAN ---
+  # Suspend to RAM after 15 min idle instead of running 24/7. While asleep the
+  # servers (Kavita/Immich/Ollama/NFS) are unreachable; wake it with a magic
+  # packet from another LAN host (`wol`/`etherwake <MAC>`, or a phone WoL app) or
+  # a keypress. Tailscale can't wake it directly — the packet is layer-2 LAN-only.
+  #
+  # CAVEAT: swayidle keys off *input* inactivity, not load. A long Ollama
+  # generation or an Immich background job with no keyboard/mouse activity will
+  # still suspend at 15 min. If that bites, add a load/inhibit guard (ask me).
+  networking.interfaces.enp9s0.wakeOnLan.enable = true;
+
+  systemd.user.services.swayidle = {
+    description = "Suspend to RAM 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'";
+      Restart = "on-failure";
+    };
+  };
+
   boot.binfmt.emulatedSystems = [ "aarch64-linux" ];
 
   # --- GPU (ROCm) ---