[PublicActivity] Admins view all activites regardless of setting

The activities are hidden on page load but any new ones will stream in regardless of the toggle admin activities setting.

Start by reproducing the admin activities toggle and tracing the PublicActivity stream that adds new activities after page load. Check how the setting is applied initially versus to incoming updates. Done means new activities remain hidden when the toggle is off and still appear when it is on.

Written by the indexing model from the issue text.