Four new extraction research documents covering PDF article thread
traversal for multi-flow magazine layouts, resource dictionary
inheritance and ResourceStack semantics for nested Form XObjects,
document catalog and page tree structure (UserUnit, Contents array,
page inheritance), and hyperlink/named destination extraction with
QuadPoints anchor text and link density classification.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
