To reproduce:

1. Open a git project with the agent sidebar, ideally with no other
threads in the sidebar.
2. Create a thread in a new git worktree and type into it without
sending.
3. While still in that worktree workspace, hit New Thread. The parked
draft must now be the last activatable entry in the sidebar.
4. Hover the parked draft → click Discard Draft
5. 💥

Release Notes:

- Fixed a panic when discarding a draft workspace.