Function headless_ownership_refusal 

pub fn headless_ownership_refusal(sop: &Sop) -> Option<String>

The refusal a headless start surface returns for a procedure whose execute steps resolve no owner. None when every step has one.

Phrased for the operator who pressed the button rather than for the author, but drawn from unowned_execute_steps — the same rule the authoring gate and the headless driver apply.