Recovered from cc-worker WIP that was left uncommitted in the dev-centre clone (card t_0055b89b). Multipart source_pdf upload at create -> source_file_id; source-pdf download endpoint resolves from exam_id (catalogue) or source_file_id. NOT yet human-reviewed/merged; preserving + verifying so it isn't clobbered. Co-Authored-By: Claude Opus 4.8 <[email protected]>