Forking a message should retain the input like in /undo #5495
Description
Feature hasn't been suggested before.
- 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.