Can't clear mention notifications on mobile app

When you get notified that you were mentioned in a thread:
1.) when you click the notification it takes you to the channel you were mentioned in but not the actual thread you were mentioned in.
2.) there is no clear way to delete notifications.
This was all in the mobile app at least

Start by reproducing a mention notification in the mobile app, checking both the destination after tapping it and the available notification actions. Trace the mobile notification flow from that behavior; done means tapping opens the mentioned thread rather than only its channel and users have a clear way to delete the notification.

Written by the indexing model from the issue text.