fix: work on making the installer work offline

installer/auto-install.nix

@@ -13,6 +13,7 @@
   ...
 }:
 {
+  # Ensure the entire system closure and all dependencies are included in the ISO
   environment.systemPackages = [
     pkgs.git
     pkgs.bashInteractive
@@ -20,6 +21,14 @@
     targetSystem
   ];
 
+  # Explicitly include the system closure in the ISO image to prevent any need to build or fetch
+  isoImage.contents = [
+    {
+      source = targetSystem;
+      target = "/system";
+    }
+  ];
+
   nixpkgs.hostPlatform = hostPlatform;
 
   systemd.services.auto-install = {
@@ -45,7 +54,13 @@
       ${diskoScript}
 
       echo ">>> Running nixos-install..."
-      nixos-install --no-root-passwd --system ${targetSystem}
+      # Use only local store - don't fetch from binary cache or build
+      nixos-install \
+        --no-root-passwd \
+        --root /mnt \
+        --system ${targetSystem} \
+        --option substitute false \
+        --option build-use-sandbox false
 
       echo ">>> Done. Rebooting."
       systemctl reboot