ca88036126
Add WebSocket listener support to NatsServer alongside the existing TCP listener. When WebSocketOptions.Port >= 0, the server binds a second socket, performs HTTP upgrade via WsUpgrade.TryUpgradeAsync, wraps the connection in WsConnection for transparent frame/deframe, and hands it to the standard NatsClient pipeline. Changes: - NatsClient: add IsWebSocket and WsInfo properties - NatsServer: add RunWebSocketAcceptLoopAsync and AcceptWebSocketClientAsync, WS listener lifecycle in StartAsync/ShutdownAsync/Dispose - NatsOptions: change WebSocketOptions.Port default from 0 to -1 (disabled) - WsConnection.ReadAsync: fix premature end-of-stream when ReadFrames returns no payloads by looping until data is available - Add WsIntegration tests (connect, ping, pub/sub over WebSocket) - Add WsConnection masked frame and end-of-stream unit tests