* feat(reviewer): surface dashboard UI link on PR reviews [INF-0000]
Post a transient "review in progress" comment (with an "Open in Web"
dashboard link) when a reviewer run starts, then delete it once the
review lands. The published review body now carries the same
"Open in Web" link, so the link persists on the review itself.
The transient comment's id is tracked in reviewer thread metadata
(status_comment_id) so it can be deleted on completion.
* refactor(reviewer): inline dashboard URL helper, drop redundant future import [INF-0000]
