Hide the new Phriction "Publish" operation behind the "Prototype" toggle

Summary: Ref T13077. This is currently a little too confusing to go out into the world, mostly because there's no way to edit documents without auto-publishing them. Keep it out of the spotlight for this release.

Test Plan: Viewed Phriction, saw publish operation marked as a prototype.

Reviewers: amckinley

Maniphest Tasks: T13077

Differential Revision: https://secure.phabricator.com/D19627