Amazon Q Chat Identification / Name

## Problem
Even with just two chats open for Amazon Q, I cannot easily tell which chat is which. I have to read some of the chat to figure it out.
## Expected behavior
I would like to be able to rename my Chat tabs so I can better keep track of the several chats I am having with you. Or, I'd like to be able to create a subject / title for each Chat and have that Subject be visible somewhere like perhaps by hovering over the Chat tab.

Start by tracing the Amazon Q chat tab entry point in the VS Code extension and how open chats are identified. Compare the requested rename flow with displaying a subject or title on each tab, then define the interaction and persistence behavior before implementing it; done means multiple open chats can be distinguished without reading their contents.

Written by the indexing model from the issue text.