feat(knowledge-corpus): implement Milestone 07 repository adapter

[adamshen1007]

Summary

• add strict shared contracts for KnowledgeOS corpus sources, immutable repository snapshots, and snapshot change sets
• materialize a validated Milestone 04 migration corpus into the existing in-memory knowledge repository
• add deterministic content fingerprints and snapshot identities, plus same-corpus refresh comparison
• document Milestone 07 architecture, acceptance criteria, and verification boundaries

Verification

• pnpm format:check
• pnpm lint
• pnpm build
• pnpm typecheck
• pnpm test — 132 tests (56 schema, 73 engine, 3 root)

Architecture and scope

@founderos/knowledge-schema owns shared corpus and snapshot contracts. @founderos/knowledge-engine owns migration-backed materialization and change detection. Existing migration and repository boundaries are preserved.

This milestone intentionally defers persistence, databases, embeddings, semantic search, retrieval ranking, knowledge graph persistence, Hermes, agents, MCP integrations, external integrations, and UI applications.

Milestone status

GO — implementation, documentation, tests, and independent review are complete.