Update the behavior of the `zed_actions::agent::AddSelectionToThread`
action so that, after the selecitons are added to the current thread,
the editor automatically scrolls to the cursor's position, fixing an
issue where the inserted selection's UI component could wrap the cursor
to the next line below, leaving it outside the viewable area.
Closes#39694
Release Notes:
- Improved the `agent: add selection to thread` action so as to
automatically scroll to the cursor's position after selections are
inserted
c42d54af17