research+feat: WebSocket support (Granian / ASGI integration) #52

Context

• WebSockets are not HTTP request/response; they need upgrade handling and a persistent two-way channel. The current stack is HTTP-only RSGI + a minimal ASGI http bridge.
• See Feature gaps.

Direction

• Research Granian + RSGI (or ASGI websocket) path: can OxyRoute expose a Python handler for connect / message / disconnect without reimplementing the server?
• If only ASGI supports WebSockets in practice, document a recommended integration (separate ASGI app vs extending oxyroute/asgi.py).

Acceptance criteria

• Design doc + spike; list what must live in Rust vs Python.
• No claim of “done” until at least one e2e test passes on a supported server.

Research

• RSGI spec for WebSocket (if any); Starlette WebSocket patterns.