Closes AI-285
Similar to how we display whether there are running threads or a thread
waiting for permission in the collapsed version of the project's header
in the sidebar, I was missing the "unread" state from being shown. I had
to change the approach here as to how we extract this information
because the previous method was relying on observing the state of the
list entries within the sidebar at every `rebuild_contents` run, and
given there aren't any list entires when the project is collapsed, it
wouldn't work.
Release Notes:
- Agent: Added the notification indicator on collapsed project headers
in the sidebar when a thread completes.
Danilo Leal
