GET /ws/agent/pending?pending_id=… runs an Ed25519 nonce-sign
handshake against the row's stored public key, then holds the
connection open. POST /api/pending-hosts/{id}/accept (admin)
mints a real Host row + bearer + AEAD-encrypted repo creds, pushes
the bearer down the open WS, deletes the pending row, and writes
a host.accept_pending audit entry. POST /api/pending-hosts/{id}/reject
closes the socket with code 4001 and audit-logs host.reject_pending.
In-memory pendingHub keyed by pending_id wires accept/reject to
their live socket.
