Image description limit warning can be rendered in a code block

If an image's description is a code block at the limit cut-off point, then the length limit message is rendered in the code block. For example, this currently occurs with the [nextcloud image](https://hub.docker.com/_/nextcloud):

<img width="784" height="833" alt="Image" src="https://github.com/user-attachments/assets/4aa6c7ba-14d9-4cac-a2d5-c1ba81af9922" />