Smoke test — migration pipeline end-to-end

Hello from the migration smoke test. If you can read this in offprint.app, the entire pipeline works end-to-end: HTML→Markdown, image rehost through our proxy, blob upload, record write with dual-body (plaintext + content[].markdown), deterministic rkey, granular scopes. Generated by /dev/smoke. Feel free to delete this record from your PDS afterwards.