Implement the MediaBoard commands and response protocol needed for
the segaboot NETWORK TEST to pass:
- TestHardware (0x0301) two-phase response via CoreTiming: phase 1
echoes test_type with 0x80 acknowledgment flag, phase 2 sends
result with testStatus=2 and checkProgress=100
- GetNetworkConfig (0x0104) with trinetcfg.bin read intercept
- Separate Execute1/Execute2 last-response buffers to prevent
cross-clobber on the shared s_media_buffer
- Generic 0x80xx cleanup command acknowledgment
- Network config persistence for SET IP ADDRESS
naari3