Makes a magic route live. The first deploy assigns the route an internal extension number and creates the routing that sends calls to its program; later deploys reuse that routing and re-enable it, regenerating it when a stored fallback destination had to be normalized. Every deploy sets the route to enabled and reloads the routing cache. Deploying an already-deployed route is safe and returns 200, and extensionNumber appears in the response only when an extension was assigned on this call.