When selecting a chat, the last-used LLM should be preselected

[struanb]

If navigating away from a chat to perform another chat, and then navigating back to the previous chat, it is counter-intuitive that the selected LLM becomes the most recently used on the other chat.

I believe it would be intuitive to select the last-used LLM on a chat, when that chat is selected. This way, continuing the chat will continue using the LLM last used on that chat.