cks-runtime v0.7.0 – add ListVersions and RevertVersion operations

Added

• ListVersionsOperation – returns a lightweight history of all versions in the current session, making the audit trail accessible to tools and LLMs.
• RevertVersionOperation – restores the Knowledge Structure to any previous version, enabling time‑travel debugging and safe rollbacks.
• ExecutionPipeline._apply_state_mutation now handles RevertVersionOperation payloads.