Implement WsCompression with Compress/Decompress methods per RFC 7692.
Key .NET adaptation: Flush() without Dispose() on DeflateStream to produce
the correct sync flush marker that can be stripped and re-appended.
Port WsConstants from golang/nats-server/server/websocket.go lines 41-106.
Includes opcodes, frame header bits, close status codes, compression
constants, header names, path routing, and the WsClientKind enum.
