Accessibility: Chat History

On Windows, all three screen readers (nvda, jaws, narrator) can't seem to be able to review chat history.
On Mac, users can review chat history but with a few issues.
1. When new message is received, you have to focus away from the chat history and come back. Then you can use up/down arrow to read the message.
2. You have to keep checking to see if you got a new message. Perhaps it would be helpful to have an option to turn on/off sound alert in setting when receiving a new message. I implemented a sound alert in my fork.
3. I'm not sure if it's a scrolling issue or what, but VoiceOver has a hard time accessing the full history (especially last messages). If you keep clearing the history after every few messages with command+e, it's more manageable. However, if you happen to clear right after receiving a new message, then you lose the message.

No source files, tests, or entry points are named. Start by reproducing chat-history review with NVDA, JAWS, Narrator, and VoiceOver on the platforms listed, then verify that new messages remain accessible, history can be fully reviewed, and any sound-alert behavior is clearly defined.

Written by the indexing model from the issue text.