Split the WB Stream provider into two orthogonal pieces:
- internal/engine/livekit — generic LiveKit transport (URL+Token only,
no service-specific assumptions). Registered as engine "livekit".
- internal/auth/wbstream — WB Stream API flow (guest register, join,
token exchange). Implements auth.Provider and auth.RoomCreator,
reports engine "livekit".
The carrier name "wbstream" now goes through registerEngineAuth, which
wires the auth provider to the engine it declares. CLI surface is
unchanged. session.Gen for wbstream calls the RoomCreator directly;
that path will become fully generic in a later step. jazz and telemost
remain on the legacy provider path for now.
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
