- Deleted _prepare_tts_context() (104 lines of duplicated logic)
- Replaced with direct build_tts_context() call in run_conversion()
- Fixed _finalize() to use raw fields (generate_epub3, epub3_book_id)
- Removed _MockJob antipattern
- Updated tests to use raw normalization_overrides field
- ConversionRequest uses raw fields instead of PronunciationConfig/Epub3ExportConfig