Function resolve_page 

fn resolve_page<'a>(
    candidates: &'a [PathBuf],
    current_page: &Path,
) -> &'a PathBuf

Pick the best candidate page for a given cross-reference lookup.

When only one candidate exists the choice is trivial. When multiple files define the same top-level name the page whose directory shares the longest common path prefix with current_page wins; ties fall back to the first entry (which is deterministic because build_name_to_page sorts before inserting).