The Arora Bridge interface.
A [Bridge] connects an Arora runtime to a remote — in practice Semio Studio
over studio-bridge. It is modelled on studio-bridge's device-client
trait: push local state changes out, receive device-info updates and
commands in, and learn when a client is asking for data.
The trait lives here (lean: arora-types + async primitives) so the runtime
can depend on the interface without depending on studio-bridge.
studio-bridge keeps its device-client implementations and provides a
connector that implements this trait.