fix(firmware): correct MR60BHA2 + LD2410 UART protocols (ADR-063)
MR60BHA2: SOF=0x01 (not 0x5359), XOR+NOT checksums on header and
data, frame types 0x0A14 (BR), 0x0A15 (HR), 0x0A16 (distance),
0x0F09 (presence). Based on Seeed Arduino library research.
LD2410: 256000 baud (not 115200), 0xAA report head marker,
target state byte at offset 2 (after data_type + head_marker).
Auto-detect: probes MR60 at 115200 first, then LD2410 at 256000.
Sets final baud rate after detection.
Co-Authored-By: claude-flow <ruv@ruv.net>
ed6157b9b7