Allow to "Continue In" Claude Agent

[bamurtaugh]

We've discussed wanting to surface the Claude Agent as an option here:

I think it'd also make sense to surface as an option from the plan mode Start Implementation dropdown (I recognize the Claude Agent has its own plan mode, but users may want to also move between the local plan mode and Claude Agent):

I know we've mentioned this as comments in other issues or threads, but I don't believe we have a dedicated issue for it, so I wanted to open this up. If it makes more sense to track in other issues though, more than happy to do that instead.

[TylerLeonhardt]

💯... I need to see how @DonJayamanne supported this in Copilot CLI.

It's another piece that feels super generic.

I mean, is it more than just "create a new chat with the immediate invocation of a summary of the previous one"?

If not, idk why any chat session provider really needs to "opt-in" to this.