Module undo 

CLI handler for ralph undo command.

Responsibilities:

• List, preview, or restore continuation checkpoints.
• Keep undo visible as a normal queue continuation workflow.
• Align wording with the canonical blocked/waiting/stalled vocabulary.

Not handled here:

• Core undo logic (see crate::undo).
• Queue lock management details beyond invoking the shared machine builders.

Structs

UndoArgs

Functions

handle

Handle the ralph undo command.