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 <noreply@anthropic.com>
c58df6715c