giga_r1_wifi Udp.read() skips first byte of UDP packets

https://github.com/arduino/ArduinoCore-mbed/blob/cdaa048b4ef1f835f8676382bba3dacbd7efe349/libraries/SocketWrapper/src/MbedUdp.cpp#L142

When parsePacket() returns non-zero, _current_packet pointer is incremented, skipping over the first byte. The function returns _current_packet[0] which is the second byte.

Start in libraries/SocketWrapper/src/MbedUdp.cpp around line 142 and trace how parsePacket() updates _current_packet before Udp.read() returns data. Verify the first byte of a UDP packet is preserved and returned rather than skipped; done when the read behavior matches the complete packet contents.

Written by the indexing model from the issue text.