Agents window: Can't use up arrow to retrieve previous chat message from history

Testing #332192

- Follow the pre-reqs in the TPI to kick off a session
- I ask a simple question `what are the first 5 lines of the readme in this repo?`
- Agent finishes its work
- ❓ Using the up arrow in chat does nothing. I expect it to populate my previous `what are the first 5 lines of the readme in this repo?` message from chat history
- In the editor window chat panel, the up arrow still seems to work as expected, so this seems Agents window specific