Function justify_pdf_seam 

pub fn justify_pdf_seam(
    prev_tail_raw: &str,
    next_head_raw: &str,
    col: usize,
) -> Vec<String>

Re-justify a seam paragraph formed by joining the trailing partial of one page with the leading partial of the next. The joined text is fed through the standard PDF justifier so soft hyphens, mid-word breaks and similar cross-line repairs happen as if the paragraph had never been split.