- CreateCloseMessage now operates on UTF-8 byte length (matching Go's
len(body) behavior) instead of character length, with proper UTF-8
boundary detection during truncation
- WsCompression.Compress now uses try/finally for exception-safe disposal
of DeflateStream and MemoryStream
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.