CLI/TUI: support editing an already-sent user message and regenerating downstream turns

What variant of Codex are you using?
CLI

What feature would you like to see?
Support editing an already-sent user message in Codex CLI/TUI, with the same semantics as VS Code Codex and ChatGPT web: edit a previous user turn, submit the edited text, and regenerate downstream turns from that point. This is not history recall, rollback/backtrack, or fork/branch. It is true post-send message editing.

Additional information
This would make CLI prompt iteration consistent with other Codex/OpenAI surfaces. The closest existing issue I found is about branching from a previous message, but that is a different workflow from editing an existing sent message in place and regenerating from there. If full support is too large initially, even a first version limited to editing the most recent user message would help.