Cartoon fronts cards have incorrect design format

A Cartoon article has a design format of `PictureDesign`. For example, if you inspect the [json](https://www.theguardian.com/commentisfree/picture/2025/feb/25/whats-the-secret-to-duttons-polling-success.json) in this [article](https://www.theguardian.com/commentisfree/picture/2025/feb/25/whats-the-secret-to-duttons-polling-success), you see that `"format": { "design": "PictureDesign", ... }`.

However, when a cartoon card is used on a front, it's design format is `Standard` instead of `Picture`.

This [PR](https://github.com/guardian/dotcom-rendering/pull/13475) is a workaround to this issue, as we should be able to use `article.format`.