fix: dev vm setup

modules/nixos/virtualization.nix

@@ -0,0 +1,31 @@
+{ lib, pkgs, ... }: {
+  # QEMU guest agent provides graceful shutdowns and metadata exchange.
+  # Disabled by default - enable in host overlay if needed.
+  services.qemuGuest.enable = lib.mkDefault false;
+
+  # Spice vdagent handles clipboard sync, display resize, and mouse integration.
+  services.spice-vdagentd.enable = lib.mkDefault true;
+
+  # Keep the VM clock in sync if timesyncd is not already enabled elsewhere.
+  services.timesyncd.enable = lib.mkDefault true;
+
+  # Ensure essential virtio drivers are available early during boot.
+  boot.initrd.kernelModules = lib.mkDefault [
+    "virtio_pci"
+    "virtio_blk"
+    "virtio_net"
+    "virtio_scsi"
+    "virtio_mmio"
+  ];
+
+  boot.kernelModules =
+    lib.mkDefault [ "virtio_balloon" "virtio_console" "virtio_rng" ];
+
+  # Provide udev rules to improve virtio device behaviour.
+  services.udev.extraRules = lib.mkDefault ''
+    ACTION=="add", SUBSYSTEM=="virtio", ATTR{device/driver_override}=""
+  '';
+
+  # Pull in a few helper tools useful when tuning the guest.
+  environment.systemPackages = with pkgs; [ spice-vdagent ];
+}