AI agent-based review flows for doc editing

[stevenle]

Description

In addition to draft and published states, we should explore having some DB folder for AI-based workflows, e.g. review.

The workflow would be something like:

• User prompts AI to make a change to a doc
• AI saves the changes to the review folder within the doc path (similar to versions), e.g. collections/BlogPosts/drafts/<slug>/reviews/<review_id>
• User can preview the CMS-based changes side-by-side via a new editor diff viewer
• User can preview the rendered page changes via a URL param (e.g. ?preview=true&review=<id>)
• To accept the changes, we would simply copy the doc from the review state to the draft state