feat: idols-akane - add virtfs file sharing between host & guest

hosts/idols-akane/default.nix

@@ -27,6 +27,9 @@ in
     "fat"
     "vfat"
     "exfat"
+
+    # for file sharing between host & guests
+    "virtiofs"
   ];
 
   boot.initrd.availableKernelModules = [

hosts/idols-akane/virtfs.nix

@@ -0,0 +1,18 @@
+{
+  fileSystems."/mnt/utm" = {
+    device = "share"; # 9p tag name from UTM/QEMU configuration
+    fsType = "9p"; # Virtio-9p filesystem type
+    options = [
+      "trans=virtio" # Use virtio transport for paravirtualized I/O
+      "version=9p2000.L" # 9P protocol version (best Linux compatibility)
+      "ro" # Read-only access
+      "_netdev" # Mark as network-dependent (waits for network)
+      "nofail" # Don't fail boot if mount fails
+      "auto" # Mount automatically with -a
+
+      # Ownership mapping - all files appear as specified user/group
+      "uid=1000" # Map to user ID 1000
+      "gid=1000" # Map to group ID 100
+    ];
+  };
+}