Option to edit previous messages

[Yahiewi]

One feature that is available in other agents that would be useful here is the option to go back to a previous message and edit it and restart the conversation from that point.
This would drop the history that comes after that message, but would also have to undo the changes made in the workspace.
Here's an example of how this is implemented in something like Copilot:

Screencast.from.2026-03-09.11-03-42.mp4

In this example, I prompt the agent to add some console logs, then when I modify that message I get a modal to confirm that I want to restore the history and code to that state.
We could do something similar, or perhaps even better would be to implement a branching history, so users don't lose their previous conversations or modifications when editing their messages.

I imagine the hardest part is undoing all of the different commands an agent can execute and I'm not yet sure how feasible this even is.
We could look at this PR for inspiration.
We might also be able to use the Jupyter checkpoint system (.ipynb_checkpoints).

[Yahiewi]

I opened PR #310 to add the option to edit messages, this feature does not however undo the code changes made by the AI agent.
I think that needs to have a separate PR if it were to happen and is not going to be straight-forward because of the considerations in the collaborative case.