Expand main/README with master/slave overview, boot config, protocols,
and build notes; point goTool README at the full system doc.
Co-authored-by: Cursor <cursoragent@cursor.com>
Framed protobuf client for /dev/ttyUSB0 at 921600 baud with generated
uart_messages types matching the device protocol.
Co-authored-by: Cursor <cursoragent@cursor.com>