Expected behavior

Attempting to view a post from a private Atomic site should show the post in the reader, just like it is done for posts from other types of sites.

Actual behavior

Attempting to view a post from a private Atomic site in Reader results in a log in screen.

Steps to reproduce the behavior

Use a fresh install of the WPiOS app

1. Log in to the app and navigate straight to the Reader
2. Choose a private Atomic site
3. Tap the ellipsis menu (three dots) next to a post and select Visit
4. Notice the login prompt

Additional info

• Discovered while testing Issues/15266 fix preview url #15309, we noticed that a "workaround" is to first visit View Site (which obtains the necessary cookies that Reader needs) and then go back to the Reader and it should now load properly. So it was noted that Reader seems to be missing logic to fetch cookies on its own.
• This is not a regression in 16.1, I reproduced it in TestFlight build 15.9.0.2

Tested on iPhone 11, iOS 14, WPiOS 16.1