Function build_reference_map 

pub fn build_reference_map(
    inf_entries: &HashMap<PathBuf, Vec<InfEntry>>,
    s2s_files: &[PathBuf],
    input_root: &Path,
) -> (S2sRefMap, S2sSectionMap)

Build a reference map: for each .s2s file, what commands reference it and how.

Scans both embedded scripts in .inf entries and standalone .s2s files. Also builds a section-level map for files referenced with section names.