Connect the Repository overview to authoritative runtime snapshots

[Traviinam]

Closes #8.

Summary

• connect the runtime-injected protocol session to the production RepositoryStore
• adapt Repository Engine refresh results into validated Repository, Worktree, freshness, availability, and Upstream snapshots
• consume authoritative snapshot and SSE invalidation updates without losing revisions during in-flight refreshes
• preserve the last good snapshot across refresh failures and expose typed non-Repository/failed states
• capability-disable Fetch entry points until the Fetch implementation lands

Verification

• npm run lint
• npm run typecheck
• npm run build
• npm test (193 tests)