feat(firmware): BNO085 node, concentrador y listener PGN 127237

AR_electronics — AR-Autopilot Project

Tarea #3 — firmware/ar_bno085_node_v1/
  Nodo compacto ESP32+CAN lee heading y yaw rate del BNO085 via I2C
  y los publica en el backbone NMEA 2000 como PGN 127250+127251 a 10 Hz.

Tarea #4 — firmware/ar_concentrador_v1/
  Gateway NMEA2000<->NMEA0183 con 4 puertos OUT (UART1 TX broadcast)
  y 4 puertos IN (UART2 RX comandos). Parsea sentencias $PARP, gestiona
  autoridad de mando entre estaciones con timeout 10s y override del puente.
  Reenvía comandos autopilot como PGN 127237 al backbone.

Tarea #5 — nmea2000_consumer (ar_autopilot_v1)
  Listener PGN 127237 entrante desde concentrador:
  HeadingControlSnapshot, HandleHeadingControl() con filtro source address,
  nmea2000_htc() publico, ventana stale 3s para comandos externos.

firmware/ar_bno085_node_v1/platformio.ini

@@ -0,0 +1,45 @@
+; =============================================================================
+; AR BNO085 Compact Node v1 -- firmware build configuration
+; =============================================================================
+;
+; Target hardware: AR-BNO085-NODE v1.0 (ESP32-DOWD, compact board)
+; Role:            NMEA 2000 IMU node -- publishes heading (PGN 127250)
+;                  and rate-of-turn (PGN 127251) from BNO085 sensor.
+;
+; Pinout:
+;   GPIO21 -- I2C SDA  (BNO085)
+;   GPIO22 -- I2C SCL  (BNO085)
+;   GPIO34 -- BNO085 INT (data-ready, active low, input-only)
+;   GPIO13 -- BNO085 NRST (output, active low, drive LOW to reset)
+;   GPIO23 -- CAN TX  (MCP2562T)
+;   GPIO4  -- CAN RX  (MCP2562T)
+; =============================================================================
+
+[platformio]
+src_dir = src
+default_envs = esp32-dev
+
+[env]
+platform = espressif32@^6.7.0
+framework = arduino
+monitor_speed = 115200
+monitor_filters = esp32_exception_decoder, time
+build_flags =
+    -std=gnu++17
+    -DCORE_DEBUG_LEVEL=3
+    -DAR_FW_VERSION=\"1.0.0\"
+    -Wall
+    -Wno-unused-parameter
+build_unflags =
+    -std=gnu++11
+lib_deps =
+    ttlappalainen/NMEA2000-library@^4.22.0
+    ttlappalainen/NMEA2000_esp32@^1.0.3
+    sparkfun/SparkFun BNO08x Cortex Based IMU@^1.0.3
+
+[env:esp32-dev]
+board = esp32dev
+build_type = release
+build_flags =
+    ${env.build_flags}
+    -Os