add more swap to cupsnet, as nix ci ooms

nixos/boxes/cupsnet/default.nix

@@ -1,4 +1,10 @@
-{ config, pkgs, inputs, lib, ... }: {
+{
+  config,
+  pkgs,
+  inputs,
+  lib,
+  ...
+}: {
   imports = [
     "${inputs.nixpkgs-stable}/nixos/modules/profiles/qemu-guest.nix"
     ../cli.nix
@@ -20,8 +26,15 @@
   zramSwap = {
     enable = true;
     algorithm = "zstd";
-    memoryPercent = 100;
+    memoryPercent = 50;
   };
 
+  swapDevices = [
+    {
+      device = "/swapfile";
+      size = 16384;
+    }
+  ];
+
   time.timeZone = "Europe/London";
 }