Application protocol over Local Peer-to-Peer transport #380

Following up on the discussion at TPAC 2026 (slides, slide 8).

With the application protocol now defined against an abstract OSP transport, it can also run over a Local Peer-to-Peer connection, i.e. over a WebTransport session to a peer the user picked. Then a site can speak Open Screen to a receiver itself, with the same messages and wire format the browser uses for the Presentation and Remote Playback APIs.

I tried this in an experimental TypeScript implementation (go-lp2p/osp-app). It still does both DataChannels (WebRTC aligned) & WebTransport (picking one is an open issue). Three questions:

1. Is this a direction the group wants to support? If so, the transport requirements in Partially address #342 and #343. #378 should hold for these transports too (see my comments there).
2. A cleaner reference implementation, and tests. Should osp-app grow into a clean, dependency-free implementation, and where should it live (here, a separate w3c repo, or stand-alone)? It could anchor a protocol conformance suite and/or Web Platform Tests for the API surfaces.
3. Making the most of LP2P. What would the application protocol want from LP2P, e.g. how a receiver treats the requesting origin and peer metadata, reconnection, etc?