Action Bar: Not available on Atomic Sites

#### Steps to reproduce
1. Access a simple site you own or where are an administrator
2. Notice the Action Bar at right-hand the lower corner of the site.
3. Open an atomic site
4. Notice it doesn't have the Action Bar

#### What I expected

To see the action bar on the atomic site. It provides a quick way to edit a page or post. A regular WordPress.org site has this option on the top bar. AT sites completely lose that quick action.

#### What happened instead

The atomic site didn't have the action bar.

#### Screenshot / Video

https://cld.wthms.co/6sebxo

#### Context / Source

This was reported by a user who already had a workflow with the action bar. And felt when upgrading to the Business plan they had to go through more steps to do the same they can on a lower plan.

#painpoint #user-report

15748514-hc

Reproduce the missing Action Bar on both a regular site and an atomic site, using the steps and screenshot in the issue. Start by locating the Action Bar entry point and the atomic-site condition; done means the bar appears on atomic sites and still provides the quick edit action. No file or test is named, so expect to trace the relevant frontend code first.

Written by the indexing model from the issue text.