Complete coordinator bead verification. All 7 child task beads closed
with full preprocessing pipeline implemented:
- Deskew via pixDeskew (Hough transform, skip < 0.3°)
- Contrast normalization (histogram stretch)
- Binarization (Sauvola for physical scans, Otsu for digital, skip for JBIG2)
- Denoising (3×3 median filter, skip for JBIG2)
- Border padding (10px white margin)
Fixtures and tests in place. PASS on all acceptance criteria except WER
benchmark (deferred to Phase 5.4 OCR integration).
Closes pdftract-1lo5.
