Archive finished chats and show them again on demand
Archive a chat when you are done with it. The session and transcript stay intact and reachable by URL; the thread just leaves the list.
In the UI: use the archive control on a row in Chats, and the Show archived filter to list archived threads. The sidebar’s All chats link stays visible even when no threads are listed.
In the API: PUT /v1/sessions/{id}/archive archives and DELETE /v1/sessions/{id}/archive restores. Both are idempotent. Session lists hide archived sessions unless you pass include_archived=true, which widens facet counts too.