Improve discoverability of archived chats

[cwebster-99]

I had trouble locating my archived chats. I originally had looked in the ⚙️, ..., and search in the Command Palette.

I remembered we use the follow practice for showing hidden terminals and I wonder if something like this would help with archived chats in the sessions view. Before figuring out how to view archived chats, it seemed deleting and archiving did the same thing.

[bpasero]

I am pushing a change to include archived sessions by default but collapsed and with their count:

Screen.Recording.2026-01-11.at.08.17.33.mov