[Feature Request] Add conversation rewind capability to revise responses at arbitrary points

Bug Description
one should be able to rewind a conversation to an AskUserQuestion prompt, to revise an answer to a question. this is really a special case of a more general feature, via which one could rewind the conversation to an arbitrary point, e.g., the middle of the previous agent output, rather than just to previous user inputs.

Environment Info

• Platform: darwin
• Terminal: ghostty
• Version: 2.1.231
• Feedback ID: 15a022a0-9bd3-4bbc-ae8e-7f14d82674e2