EntityField.format gains 'image' | 'avatar' | 'thumbnail'. When set, mock
generation returns a deterministic https://picsum.photos URL keyed on
entityName + fieldName. Field-name fallback also covers imageUrl, photo,
avatar, thumbnail, picture, cover, banner (and *Url variants) so existing
schemas without an explicit format annotation get real photos instead of
faker.lorem.words().

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>