pdf = "data/nist/NIST.SP.800-207.pdf"
line_df = fitz_pdf_to_line_df(pdf)
span_df = build_span_df(pdf)
enriched = enrich_line_df_with_style(line_df, span_df)   # per-line font + bold
candidates = detect_body_headings(enriched, threshold=3.0)

page = 10
for _, row in candidates[candidates["page_num"] == page].iterrows():
    print(row["text"], row["heading_score"], row["candidate_level"],
          row["font_size"], bool(row["is_bold"]))
# 1 Introduction 4.28 1 12.0 True