Documents the agents plan rollback command (CLI entry at src/cleveragents/cli/commands/plan.py) that was integrated into master under Epic #8493. The command provides checkpoint-based plan state restoration, allowing plans to be restored to a previous checkpoint and resuming execution from that point. CHANGELOG.md entry added under [Unreleased] > ### Added section; CONTRIBUTORS.md updated with HAL 9000's contribution for this checkpoint-based rollback feature.
ISSUES CLOSED: #8557
Epic: #8493