fix(masque): address review findings for PR #76

- Return errors from MasqueConn.Read/Write instead of silently
  succeeding (prevents infinite busy-loops and silent data loss
  if these methods are accidentally called).
- Set recorder Network field in protocol dispatch switch rather
  than hardcoding "udp", so early errors don't misreport type.
- Clarify that DatagramConn context-ID handling only supports
  context ID 0 (sufficient for CONNECT-UDP per RFC 9298).

dialer/http3/masque/client.go

@@ -3,6 +3,7 @@ package masque
 import (
 	"context"
 	"crypto/tls"
+	"errors"
 	"net"
 	"time"
 
@@ -11,6 +12,8 @@ import (
 	"github.com/quic-go/quic-go/http3"
 )
 
+var errReadWriteNotSupported = errors.New("masque: direct Read/Write not supported on MasqueConn, use GetRequestStream")
+
 // Client manages HTTP/3 connections for MASQUE proxying.
 // It wraps a QUIC connection and HTTP/3 client, following the session pattern
 // used by other gost dialers (ssh, quic, mws, etc.).
@@ -105,17 +108,15 @@ func (c *MasqueConn) GetHost() string {
 }
 
 // Read implements net.Conn but is not used for MASQUE.
-// The actual data transfer happens via datagrams.
+// The actual data transfer happens via datagrams or the request stream.
 func (c *MasqueConn) Read(b []byte) (n int, err error) {
-	// This should not be called - datagrams are used for data transfer
-	return 0, nil
+	return 0, errReadWriteNotSupported
 }
 
 // Write implements net.Conn but is not used for MASQUE.
-// The actual data transfer happens via datagrams.
+// The actual data transfer happens via datagrams or the request stream.
 func (c *MasqueConn) Write(b []byte) (n int, err error) {
-	// This should not be called - datagrams are used for data transfer
-	return len(b), nil
+	return 0, errReadWriteNotSupported
 }
 
 // Close closes the connection.