PatreonClient: cookie-auth requests session, /api/posts cursor pagination,
JSON:API included flattening, per-post media extraction (images/image_large/
attachments/postfile/content) with filehash dedup, loud drift detection.
Zero per-file HEADs — every media URL+file_name comes from the API. Not yet
wired into download_service (later step). Pure-parsing unit tests + fixture.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
