Function encodeMACFrame

IEEE Std 802.15.4-2020, 7.2.2 (General MAC frame format) 05-3474-23 R23.1, Annex C.2 (Zigbee MAC frame subset)

SPEC COMPLIANCE NOTES:

• ✅ Emits canonical MAC frames with Zigbee-safe payload length and CRC tail
• ✅ Shares encoding path with general 802.15.4 data while honouring Zigbee restrictions
• ⚠️ Assumes caller already prepared payload within MAC safe size DEVICE SCOPE: All logical devices.