feat(firmware): ADR-063 mmWave sensor fusion — full implementation

Phase 1-2 of ADR-063:

mmwave_sensor.c/h:
- MR60BHA2 UART parser (60 GHz: HR, BR, presence, distance)
- LD2410 UART parser (24 GHz: presence, distance)
- Auto-detection: probes UART for known frame headers at boot
- Mock generator for QEMU testing (synthetic HR 72±2, BR 16±1)
- Capability flag registration per sensor type

edge_processing.c/h:
- 48-byte fused vitals packet (magic 0xC5110004)
- Kalman-style fusion: mmWave 80% + CSI 20% when both available
- Automatic fallback to CSI-only 32-byte packet when no mmWave
- Dual presence flag (Bit3 = mmwave_present)

main.c:
- mmwave_sensor_init() called at boot with auto-detect
- Status logged in startup banner

Fuzz stubs updated for mmwave_sensor API.
Build verified: QEMU mock build passes.

Co-Authored-By: claude-flow <ruv@ruv.net>

firmware/esp32-csi-node/main/CMakeLists.txt

@@ -2,6 +2,7 @@ set(SRCS
     "main.c" "csi_collector.c" "stream_sender.c" "nvs_config.c"
     "edge_processing.c" "ota_update.c" "power_mgmt.c"
     "wasm_runtime.c" "wasm_upload.c" "rvf_parser.c"
+    "mmwave_sensor.c"
 )
 
 set(REQUIRES "")