feat: tool for user prompts

[shikokuchuo]

The new file writing capabilities are really first rate!

I attempted this in a prompt: "Ask for permission before overwriting any existing files."

It finishes with the question and ends the turn.

I can get it to continue by manually providing:

chat$chat("I approve")

But it might be useful to have another tool that lets it prompt the user, and registers the response.

We should be careful to limit the usage to where it's explicitly asked for like in my example, otherwise it would be annoying for it to break up these nice agentic tool call flows.

I can also see that within a chat session or a chat app, this won't really apply, apart from if we wanted to highlight the fact that it wants user input.