Function diff_documents 

pub fn diff_documents(
    base_pages: &[PageText],
    tailored_pages: &[PageText],
    granularity: DiffGranularity,
) -> DocumentDiffResult

Compares two documents page-by-page and returns structured diff highlights.

Note: total_differences represents the aggregate count of highlight bounding box spans rendered across both base (deletions/replacements) and tailored (insertions/replacements) pages.