Firmware simulation, Unity project, and sim-verified robot fixes

Simulation
- sim/: the unchanged robot firmware compiled into hexapod_sim.dll
  against PC stand-ins (Arduino, Servo, Wire + register-level MPU6050,
  RF24 with matching-config radio), a kinematic body model (support
  plane + planted-foot odometry) that also drives the simulated IMU,
  and a headless smoke test (sim_smoke). build.ps1 builds and tests.
- Hexapod_Simulation_Unity/ folded in (history kept in a bundle
  outside the repo). Assets/HexapodSim loads the DLL, drives the
  existing leg rig, and offers joystick / keyboard / robot-serial
  input plus a test panel.

Robot (all found or confirmed in the simulation)
- Config.h geometry taken from the Unity model.
- IK femur elevation sign, gait stance direction, body pose
  rotation direction, yaw lever arm.
- Stance feet integrated from the current command; gait restarts at
  mid-stance; heading integrates the applied turn rate, only while
  walking.
- Leg clearance and reach checks (Limits::feetFeasible); walk command
  and body pose scaled as a whole, pose scale rate-limited, planted
  feet guarded so the body never snaps or legs collide.
- Robot-gyro self-leveling as an integrator.
- Heading mode: steering relative to the body; S walks backward.
- Standing height from the remote (STANCE_HEIGHT_RANGE_MM).

Protocol v3 (reflash both boards)
- CmdPacket gains body_height (22 bytes).

Remote
- Height slider (Nextion hHeight/nHeight, serial [ ]).
- Fixed unspecified I2C read order in RemoteIMU.

LEGACY/: owner's old Nextion HMI and remote hardware assets.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

2026-current/remote/remote.ino

@@ -34,17 +34,17 @@ static void printStatus() {
                 imu.ok() ? "ok" : "MISSING", imu.rollDeg(), imu.pitchDeg());
   Serial.printf("radio %s  link %s  %u%%\n", radio_link.present() ? "ok" : "MISSING",
                 radio_link.linkOk() ? "OK" : "DOWN", radio_link.qualityPct());
-  Serial.printf("armed %d stand %d gait %s mode %s rstick %s remote_gyro %d robot_gyro %d speed %u->%u\n",
+  Serial.printf("armed %d stand %d gait %s mode %s rstick %s remote_gyro %d robot_gyro %d speed %u->%u height %d\n",
                 state.armed(), state.standRequested(), state.gaitWave() ? "wave" : "tripod",
                 state.modeB() ? "B" : "A", state.rstickXlate() ? "xlate" : "rot",
-                state.remoteGyro(), state.robotGyro(), state.speedTarget(), state.speedCurrent());
+                state.remoteGyro(), state.robotGyro(), state.speedTarget(), state.speedCurrent(), state.height());
   sticks.printCalibration(Serial);
 }
 
 static void dumpPacket(const CmdPacket& p) {
-  Serial.printf("#%3u vx %5d vy %5d yaw %5d | r %5d %5d %5d | tilt %5d %5d | spd %3u flags %02X\n",
+  Serial.printf("#%3u vx %5d vy %5d yaw %5d | r %5d %5d %5d | tilt %5d %5d | h %5d spd %3u flags %02X\n",
                 p.seq, p.vx, p.vy, p.yaw_rate, p.rx, p.ry, p.rz,
-                p.remote_roll, p.remote_pitch, p.speed_scale, p.flags);
+                p.remote_roll, p.remote_pitch, p.body_height, p.speed_scale, p.flags);
 }
 
 static void pollInputs(uint32_t now_ms) {