CLI: Add /rewind checkpoint restore that reverts both chat context and Codex-applied code edits #11626

What variant of Codex are you using?

CLI

What feature would you like to see?

Add a native /rewind checkpoint flow that restores both:

• conversation state
• Codex-applied workspace edits

from the same selected checkpoint.

Current behavior: Esc rewind only rewinds conversation/history (fork point), but does not revert code changes made after that point.

Requested behavior:

• /rewind shows recent checkpoints with:
  • timestamp
  • prompt snippet
  • files changed
• Selecting a checkpoint rewinds chat and reverts Codex-made edits after that checkpoint.
• Provide a pre-apply preview of file changes to be reverted.
• Allow editing the restored prompt before resubmitting.

Safety requirements:

• Only revert Codex-created edits after the selected checkpoint.
• Do not touch unrelated local changes that existed before checkpoint creation.
• If any file cannot be cleanly restored, show conflicts and require explicit confirmation before partial apply.

Additional information

Repro for current gap:

1. Ask Codex CLI to modify files.
2. Press Esc twice to rewind a prior user message and fork.
3. Conversation rewinds, but prior file edits remain in the working tree.

Workarounds today (/diff, !git diff, manual git restore/reset) are useful but fragmented. A unified checkpoint rewind would make iterative prompting much safer and faster.

Related context: #9203, #4487, #8819.