Implements the converter that transforms PP-StructureV3 OCR results into
the UnifiedDocument format, enabling consistent output for both OCR and
direct extraction tracks.
- Create OCRToUnifiedConverter class with full element type mapping
- Handle both enhanced (parsing_res_list) and standard markdown results
- Support 4-point and simple bbox formats for coordinates
- Establish element relationships (captions, lists, headers)
- Integrate converter into OCR service dual-track processing
- Update tasks.md marking section 3.3 complete
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Co-Authored-By: Claude <noreply@anthropic.com>
