testing/cross_backend/ws_envelope.ts

Cross-process suite for the WebSocket read loop's frame envelope — what each spine answers to a frame before anything dispatches, pinned over a real upgrade. The HTTP twin is rpc_adversarial's envelope cases (create_rpc_envelope_cases); a socket classifies its frames in its own loop (TS register_action_ws, Rust fuz_realtime's ws_endpoint), so the HTTP pins say nothing about it.

• a parse error — a frame that is not JSON answers parse_error with id: null, and the socket keeps serving
• a non-object frame — a JSON scalar answers invalid_request with id: null (the scalar is not read as its own id)
• a batch array — answers one invalid_request with id: null; batches are not supported on either transport
• a notification — a string method with no id answers no frame
• a stray response — a {id, result} frame matching no server-initiated request answers no frame (it demuxes as a peer response and is dropped)
• cancel — the notification answers no frame: for an unknown id, for malformed params, and for a request in flight, which keeps running and answers under its id once it completes (neither spine's peer/ping observes its signal, so the cancel's effect is invisible here; consumer suites with a signal-observing seam pin it)

Silence is asserted positively: each case marks the received-message count, sends its frames, then round-trips a heartbeat probe and reads back everything after the mark. The socket is ordered, so a frame that should produce nothing leaves exactly the probe's response, and the probe doubles as proof the socket survived the frame.

Wire codes are independent copies of the producers' constants — parity by test. Gated on capabilities.ws; the in-flight cancel also on capabilities.peer_request (it holds a request with peer/ping).

Cross-process only: create_ws_transport needs a real bound socket, so wire it from a *.cross.test.ts file.