feat(knowledge-registry): implement durable snapshot registry

[adamshen1007]

Summary

• add strict durable snapshot registry contracts and canonical persistence records
• implement governed lifecycle, review, approval, activation, replay, integrity, and recovery workflows
• add adapter-neutral orchestration with a local file-backed single-writer implementation
• add deterministic derived-index rebuilding and comprehensive path/source isolation
• document Milestone 09 architecture, acceptance criteria, and operational limits

Verification

• pnpm format:check
• pnpm lint
• pnpm build
• pnpm typecheck
• pnpm test (308/308)
• two independent whole-branch reviews: GO

Scope

Database persistence, embeddings, semantic search, ranking, graph persistence, Hermes, agents, MCP, integrations, and UI remain deferred.