Allow to rename local chat sessions

[schlp]

pre v0.35.0 it was possible to rename chat session. Now with the new chat session view it becomes more interesting to jump between chat sessions but makes it harder to track them. I would love to be able to rename my chat sessions again.
In addition, either adding a tag or linking a chat session to a branch would be great

[jamesmontemagno]

I would break this into several smaller feature requests, Maybe leave this one as just "rename chats", and agreed.

[justschen]

we brought back renaming in insiders, but am unsure if this will get added back in the stable build!

[bpasero]

Yes, you can use insiders to rename again, but its limited to local chat sessions for now (it used to be).

Can you try to reproduce with our nightly insider builds? You can give our preview releases a try from: https://code.visualstudio.com/insiders/

[eleanorjboyd]

seeing that rename is possible but the UI doesn't get updated till the sidebar refreshes
https://github.com/user-attachments/assets/207795a8-3d07-4fee-a280-ded608cf2275