When documents are processed through GraphRAG pipeline, coordinate
enrichment produces text_bbox (paragraph-level coordinates) instead of
char_positions (character-level OCR coordinates). Added resolveCharPositions()
helper that converts text_bbox to CharPosition[] format, enabling PDF
highlight rendering for GraphRAG-processed documents.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>