Track skill and workflow improvements

Track skill and workflow proposal impact, including rejected changes\n\nReference paper: WikiSkill: Compiling Agent Experience into Persistent Knowledge for Skill Evolution\n- arXiv: https://arxiv.org/abs/2608.27454\n- (link not exported) PDF: https://arxiv.org/pdf/2608.27454\n\nContext:\nWikiSkill (link not exported) preserves lessons from both accepted and rejected skill proposals. Hive should retain evaluation knowledge even when a skill or workflow edit is rolled back.\n\nDesired outcome:\nDesign and implement a durable skill-impact record, likely under the project wiki, recording the proposed change, motivating evidence, evaluator, benchmark or review result, acceptance/rejection decision, rollback reason, and links to relevant tasks/commits.\n\nAcceptance criteria:\n- A documented record format with stable identifiers and provenance.\n- Accepted, rejected, superseded, and rolled-back outcomes are representable.\n- Rejected proposals retain their learned evidence without changing the active skill.\n- Refresh/compile behavior is deterministic and concurrency-safe.\n- Tests cover the lifecycle and malformed/incomplete records.\n- Documentation includes at least one accepted and one rejected example.