Forking a message should retain the input like in /undo

[JosXa]

Feature hasn't been suggested before.

• [x] I have verified this feature I'm about to request hasn't been suggested before.

Describe the enhancement you want to request

When I click one of my previous messages and fork, I expect that message's content to be taken into the new session. Case in point: When your conversation only contains a single message (yours) and the LLM is working on it, then forking and having a completely empty history makes no sense at all.

I would expect clicking fork to behave the same way as undo, where it puts the message you clicked into the input box.

Use case: Try one prompt against different models to compare performance.

[github-actions[bot]]

This issue might be a duplicate of existing issues. Please check:

• #4186: "revert message" should place reverted message in the prompt input - similar feature request about placing message content in the input box
• #3071: "/timeline UX is confusing" - related issue about timeline behavior and message editing

Feel free to ignore if none of these address your specific case.