WebSocket proxy throws when forwarding reserved close code 1006

When the proxy receives a close event with code 1006 (or other reserved codes), it forwards that code with ws.close(event.code, event.reason).

This throws at runtime: TypeError: Invalid WebSocket close code: 1006

What I observed:

• one side of the WebSocket closed with code 1006
• proxy tried to forward 1006 directly
• request handling hung after the exception

Expected behavior:

• reserved close codes are not sent in outbound close frames
• proxy closes with a valid fallback code instead

Related PR: #259