feat(plan-correction): implement correction data model and persistence

Implement CorrectionRepositoryProtocol in the domain layer as the port
for correction attempt record persistence. The protocol defines CRUD
operations (create, get, list_by_plan, update_state, delete) following
the clean architecture pattern with dependency inversion.

Removes out-of-scope checkpoint CLI code (issue #8559) that was
accidentally included in this PR, which caused undefined Behave step
failures in CI. Aligns CHANGELOG.md and CONTRIBUTORS.md with the
actual delivered scope.

ISSUES CLOSED: #8531

CONTRIBUTORS.md

@@ -22,6 +22,7 @@ Below are some of the specific details of various contributions.
 * HAL 9000 has contributed the plugin entry point security hardening fix (#7476): enforced entry point allowlist validation before importing plugin modules to prevent malicious plugin loading.
 * HAL 9000 has contributed the benchmark workflow separation (#9040): moved the benchmark-regression job out of the default PR workflow into a dedicated scheduled workflow, reducing median PR CI turnaround time from 99-132 minutes to under 30 minutes.
 * HAL 9000 has contributed the agent-evolution-pool-supervisor PR metadata assignment (#7888): the supervisor now automatically looks up the Type/Automation label and earliest open milestone before dispatching improvement PR creation workers, ensuring all generated improvement PRs have correct Type labels and milestone assignments.
+* HAL 9000 has contributed the correction data model domain protocol (PR #8685 / issue #8531): implemented `CorrectionRepositoryProtocol` as the domain port for correction attempt record persistence, enabling the Plan Correction Engine (v3.2.0) to persist correction attempts durably across operations.
 * This project was made possible thanks to considerable donation of time, money, and resources by CleverThis, Inc.
 * HAL 9000 has contributed automated bug fixes, CLI output formatting improvements, and ongoing maintenance as part of the CleverAgents automation system.
 * HAL 9000 has contributed the file edit encoding parameter fix (PR #8258 / issue #7559).