Feature: continue conversation when using TUI

[duluk]

I have made a modification to keep the conversation with the TUI going by default. It's essentially a for loop which resets certain fields, and sets ContinueLast to true so that the conversation will maintain context.

If the prompt is passed as a CLI argument, it ends as normal.

As noted in my previous issue, I am creating an issue prior to creating a PR per the Contributing Guidelines.

[caarlos0]

hey! if you want to contribute that, I would happy to review it and maybe merge :)