Adds a top-level hub/ package that hosts an EdgeSync hub in-process: fossil hub repo bootstrap, embedded NATS server with JetStream, auto-port allocation, libfossil HTTP server (timeline UI + xfer endpoint), user management, and hub-side commits/reads. All libfossil and nats-server types are wrapped internally — the public surface exposes only stdlib types and types defined here.

Public API: - Config + NewHub + ServeHTTP + Stop - NATSURL / LeafUpstream / HTTPAddr accessors - AddUser / GetUser / HasUser / ListUsers / RemoveUser (User type) - Commit / Read / ReadAt (RevID, FileToCommit, CommitOpts types)

Auto port allocation: passing 0 for FossilHTTPPort, NATSClientPort, or NATSLeafPort yields three distinct bound ports. The HTTP listener is bound during NewHub so HTTPAddr() is immediately usable, even before ServeHTTP is called.

SQLite tuning (SetMaxOpenConns(1) + busy_timeout=30s) applied at hub bootstrap, matching the leaf agent's tuning.

Lives inside the EdgeSync root module (not a separate go.mod) so it ships in lockstep with the leaf agent. Can be promoted to its own module later if downstream consumers need to depend on it independently.

Closes #102 check-in: 67ea682587 user: [email protected] tags: trunk