All 4 children beads closed with verification:
- Line struct + baseline computation (pdftract-sdx9z)
- Baseline clustering algorithm (pdftract-6bwq4)
- Within-line span sorting (pdftract-1jkme)
- RTL direction detection (pdftract-1ofnz)
Acceptance criteria:
- ✅ All 4 children closed
- ✅ Two-column layout: columns NOT merged into one line (test_two_column_separate_blocks)
- ✅ Superscript span at higher y: clustered with baseline text
- ✅ Arabic text: bidi R characters detected, spans sorted right-to-left
- ✅ Mixed Latin+Arabic line: detected as "mixed" direction
44/44 tests pass in layout::line module.
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
