- Add TAGGED_PDF_STRUCT_TREE_DEFERRED diagnostic emission for tagged PDFs
- Set reading_order_algorithm to xy_cut for all PDFs in v0.1.0-v0.3.0
- Diagnostic emitted once per document (not per page)
- Add tests for tagged and untagged PDF behavior
- Phase 7.1 will replace with real StructTree traversal
Closes: pdftract-5tvv1
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
