While the previous fix in the stack helped for custom roles / roles that will be edited, the permissions for Admins is set in thread-permissions.js. This diff addresses the change that will be needed to fix permissions for Admins. Essentially, we remove the descendant_voiced permission from Admins so they need to click the 'Join chat' button first in order to 1) 'become a member' and 2) send messages. Before this change, an Admin would see both 'Join chat' and also the chat input bar.

Resolves https://linear.app/comm/issue/ENG-5180/join-chat-mode-showing-chat-input-field

Depends on D9493

Going to add @ashoat as blocking since I think he has the most permissions context and also since this change will affect his role the most (a migration will be required to modify the existing role, but this change should take affect for newly created communities)

Confirmed that for Admins exclusively (tested other roles in the previous diff):

• Before this change, Admins could see 'Join chat' but also type in the chat bar
• After this change, Admins will see only one or the other

Also fixed up the unit tests to match this behavior and ran yarn workspace lib test