Adds hub.OpenRepo(path) (*Repo, error) — a server-less handle for one-off CLI invocations and short-lived helpers (bones #186 needs this for `bones hub user list`, `bones plan finalize`, and slot-user provisioning, all of which currently drop to direct libfossil.Open because hub.NewHub spins up a redundant NATS server every time).

The new *hub.Repo type holds the libfossil handle and carries every user / commit / read method that *hub.Hub used to define on itself. *hub.Hub now holds a *hub.Repo internally and one-line-delegates each method, so both code paths share method bodies — no duplication.

Adds Hub.Repo() *Repo accessor for sharing the live handle out of a running hub. Documented contract: don't call Close on a *Repo returned by Hub.Repo while the Hub is still serving — Hub.Stop is the right teardown for that case. Repo.Close is idempotent so accidental double- close from teardown ordering is safe.

Tests: - TestOpenRepo_RoundTrip — every *Repo method against a path bootstrapped by NewHub. Same observable state. - TestOpenRepo_RejectsEmptyPath, TestOpenRepo_RejectsMissingPath. - TestRepo_Close_IsIdempotent. - TestHub_Repo_AccessorReturnsLiveHandle — operations on the *Repo accessor are observable via the *Hub.

Closes #131 check-in: 5f025def67 user: [email protected] tags: trunk