Webp image not supported in ai ckeditor dialogues image uploads

Problem/Motivation

Webp images are not supported in ai ckeditor dialogue modal

Steps to reproduce

Edit an existing node: go to /node/[nid]/edit.
In a CKEditor field (e.g., a body or description field), open an AI plugin dialog that includes a file upload element (e.g., an "Insert Image" button with AI enhancement).
Attempt to change the image to webp image in the modal (for example, select or upload an image or trigger the AI generation).

Proposed resolution

Remaining tasks

User interface changes

API changes

Data model changes