Improve confirmations and hints for mutations

1. When confirming --yes via tty, show the diff.
1. Hint an undo command upon a successful mutation.

No files or tests are named. Start by locating the CLI paths that handle --yes confirmations through a tty and successful mutations; verify the confirmation displays the diff and that a completed mutation prints an undo command.

索引モデルが issue の本文から書いたものです。