Block::isPlaceholder replaces the divi/placeholder literals (ledger T4); NodeIndex::parentBlock/sectionLabel replace the two parentBlock copies and DiviWriter::sectionLabel; DiviChange::idOf and Outline::summary replace the duplicated id resolution and outline text; DiviSchema holds the shared input properties. Behaviour unchanged. Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01At3V6SjwbMe6eMzVGW3Hs7