The _detect_spine_shadow function was triggering on normal text content
because shadow_range > 20 was too low and convolution edge artifacts
created artificially low values. Now requires: range > 40, darkest < 180,
narrow valley (not text plateau), and brightness rise toward page content.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
Spalten-, Zeilen-, Woerter-Overlay und alle nachfolgenden Steps
(LLM-Review, Rekonstruktion) lesen jetzt image/cropped mit Fallback
auf image/dewarped. Tests fuer page_crop.py hinzugefuegt (25 Tests).
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>