Function check_generated_pages 

fn check_generated_pages(root: &Path) -> Vec<Error>

Check 3: no generated page under docs/ publishes a site-absolute URL.

The list comes from the generator registry rather than from a constant, so it covers a page added after this command was written.

This is the check generate-all --mode check cannot make, and the bite test measured it: removing the rewrite call from run_one and re-running --mode write leaves --mode check green — the file on disk equals what the generator now produces — while four pages carry the absolute URL again. --mode check asks “is the page what the generator writes?”; this asks “is what the generator writes correct?”, and a regression in the rewrite itself is only visible to the second question.