Function promote_to_corpus 

pub fn promote_to_corpus(
    src: &Path,
    dest_dir: &Path,
    force: bool,
) -> Result<PathBuf>

Promote an import draft (or any review markdown) into the published corpus after check.

Copies src → dest_dir/{stem}.md. Never overwrites unless force. Source is left in place (human deletes import drafts after review).