Client orchestrates the two-step push/pull protocol: manifest exchange
followed by chunked blob streaming. Push detects server-newer (returns
ErrServerNewer) and up-to-date states. Pull computes missing blobs
locally and streams only what's needed. Prune delegates to server RPC.
6 integration tests via in-process bufconn server.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
