Reduce the assumptions in the default template

[xdbr]

I think the assumptions of the default template should be reduced at least by the xserver component and maybe as well for the VM.

In my case, I let everything run on a headless server, so the xserver part is too much to assume

As far as I can see, one could:

• either make these parts opt-in and keep a simpler profile for the general case – or –
• create another template entirely (e.g. server-template, desktop-template)

[This is a reminder issue as per ref https://github.com//pull/80#issuecomment-3525793292]

[vic]

GUI is opt-out. Since believe most users will want a GUI to kickstart their configs.

For using TUI (Console) edit modules/vm.nix inside your default-template copy.