firmware: expand sensor telemetry

docs/CHANGELOG.md

@@ -8,6 +8,7 @@
 - Silently discard malformed partial RS485 echoes instead of emitting recursive `invalid_json` responses.
 - Replaced sensor auto-detection with the verified installation settings: BNO086 address `0x4B` and MAX-M10S UART at 38400 baud.
 - Added fixed-address BNO086 power-up retries, runtime recovery, and report restoration after sensor resets.
+- Expanded telemetry with BNO086 motion/gravity/stability reports and GPS HDOP/data ages.
 
 ## Unreleased
 

docs/SENSOR_NODE_PROTOCOL.md

@@ -8,8 +8,8 @@ The expansion-board pins are D2 driver enable, D4 TX, and D5 RX. Only physical b
 
 `sensor_status` includes `node_id`, `firmware_version`, `uptime_ms`, and:
 
-- `imu`: `online`, `valid`, `accuracy`, quaternion, yaw, pitch, and roll in degrees.
-- `gps`: `online`, `fix`, satellites, NMEA character/checksum counters, latitude, longitude, altitude meters, speed kph, course degrees, and structured UTC.
+- `imu`: rotation data plus linear acceleration, angular velocity, gravity, stability classification, and per-report accuracy/age.
+- `gps`: existing navigation data plus HDOP and location/time ages.
 
 `online` only means UART bytes arrived recently. In `gps.nmea`, a rising `sentences_passed` count proves valid NMEA at the configured baud rate. A rising character count with no passed sentences indicates wrong-baud noise or malformed data. A consistently rising failed count indicates corrupt UART data or a baud mismatch.