Bun parity: preserve WebSocket proxy control-frame liveness

Parent: #66 Predecessor: #389

Corpus position 4202/4708: js/web/websocket/test-ws-bidir-proxy.test.ts.

Home must preserve client/server ping and pong delivery through the TLS proxy compatibility path, automatically answer ping frames, retain buffered control frames, and surface invalid socket-state operations with stable error metadata.

Acceptance criteria:

• unchanged upstream file passes 1/1
• no failed, todo, unsupported, or allowed-empty classification
• permanent regression covers bidirectional proxy control-frame liveness
• errors include stable code, operation, and ready-state context

Implementation: 8deff4c.

Completed and pushed in 8deff4c (fix(websocket): preserve proxy control-frame liveness).

The unchanged upstream proxy test is 1/1 green with zero fallback classifications. Home now preserves ping/pong events in both directions, supplies automatic pong behavior, buffers partial control frames, and reports invalid operations as ERR_WEBSOCKET_NOT_OPEN with operation and ready-state context. The permanent regression passes.