Four new extraction research documents covering cross-reference table
and xref stream parsing with error recovery, PDF object model and lexer
correctness (all 8 types, string escapes, stream /Length recovery),
FontDescriptor fields and embedded font data (Type1/TrueType/CFF/OT),
and PDF/UA-2 / PDF 2.0 structure changes (MathML, NFC normalization,
new structure types, artifact classification improvements).
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
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