ACAT – All Creatures Are Traitors – an April Fool's mod from 2022.

fktifzobr, all files within the game's archives have the "Read-only" attribute, and directly modifying them won't allow you to save the changes. It's a simple protection against careless users; therefore, the only solution is to copy and paste them to the desktop and then back. Alternatively, you can simply remove the "Read-only" attribute from all archives and the files within: copy all the data to the data~cash folder, apply the removal of the "Read-only" attribute to all files there, and then repack them.