The classify_heading function was already implemented in
crates/pdftract-core/src/layout/line.rs (lines 666-722).
All acceptance criteria verified:
- 18pt block, body 12pt, 1 line: Heading (1.5 > 1.2) ✓
- 14pt block, body 12pt, 1 line: NOT (1.17 < 1.2) ✓
- 18pt block, 3 lines: NOT (too many lines) ✓
- 12pt block, body 12pt: NOT ✓
All 10 heading classification tests pass with nextest.
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
