Document session error

[ellisonbg]

When I leave JupyterLab open for a while with an RTC doc open, I eventually get this dialog. When I close it, I can tell that RTC sync is no longer working.

If I refresh the page, it goes back to working.

[dlqqq]

From standup:

1. This PR may be relevant: Periodically update the persona awareness to keep it alive jupyterlab/jupyter-ai#1358

2. We should check the WS close code when this happens. That will give us a little more info to work with.

[dlqqq]

I did manage to reproduce this by doing the following:

1. Create a new asdf.chat
2. Run rm asdf.chat
3. Refresh and try creating a new asdf.chat file

However this may just be due to the fact that jupyter-chat does not handle the out-of-band change signals that we emit via the WS close code.