Confirmation preview enumerates every side-effect (plan-level label creation,
assignee diff, bucket move, checklist truncation) so nothing happens that
wasn't shown on the card. Explicit-but-missing labels trigger a 3-button
choice (register / drop / cancel) since creating them mutates the Plan's
categoryDescriptions.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
