Function linkify 

pub fn linkify(
    body: &str,
    current_dir: &Path,
    index: &HashMap<String, (String, PathBuf)>,
    re: &Regex,
) -> String

Rewrite bare FEAT-XXXX/WI-XXXX mentions (and refresh existing opys links) in body prose into [ID — Title](relpath). Idempotent; references inside fenced code blocks, inline code spans, or existing markdown link syntax (label or destination) are left untouched, and a mention whose target is absent from index is left as-is.