Change Stable Diffusion/NAI Diffusion from artist to meta tags

Posted under Tags

The bulk update request #12819 has been approved by @evazion.

category stable_diffusion -> meta
category nai_diffusion -> meta

These should be treated as meta tags, not artist tags. The person who generated the image should be tagged as the artist, not the AI.

I see people removing artist tags from AI-generated posts out of the belief that AI artists don't deserve to be credited as real artists. Okay, fine. But for Danbooru purposes, we need to know who created the work. We need to be able to look up the artist's Pixiv and Twitter accounts so we can tell whether they're an AI artist or not. We need to be able to find other posts by the same artist so we can tag them as AI-generated too. We need to be able to make artist entries for AI accounts so we can warn people not to upload from them. Removing the artist tag only makes these things harder.