Extract DEAD_DECAY_FACTOR and SENSOR_SANITY_LIMIT_MT to Config.h

Two feel-tuning magic numbers hardcoded by PR sb-ocr#3:
- MotionController.cpp - 0.8f per-tick decay factor applied to the
  Kalman estimate when the current measurement is below the dead
  zone.
- SensorController.cpp - 500.0f mT outer bound for the sensor
  sanity check. EXTRA_SHORT_RANGE actually peaks around 130 mT;
  the note about that is moved into the Config comment where it
  is discoverable.

Both now live in Config.h alongside the other user-tunable knobs
(KALMAN_Q, KALMAN_R, SENSITIVITY_EXP, etc.) as DEAD_DECAY_FACTOR
and SENSOR_SANITY_LIMIT_MT.

Author: arekm

firmware/include/Config.h

@@ -43,6 +43,15 @@ const float KALMAN_R = 4.0;
 // 1.0 = linear, 3.0 = cubic (fine control at small deflections, fast at large).
 const float SENSITIVITY_EXP = 3.0;
 
+// Per-tick multiplier applied to the Kalman estimate when the measurement
+// is below the dead zone. Lower = faster decay to zero, 1.0 = no decay.
+const float DEAD_DECAY_FACTOR = 0.8;
+
+// Sensor validation: reject any frame where a magnetic axis reads beyond
+// this magnitude. EXTRA_SHORT_RANGE peaks around 130 mT; anything past
+// this bound indicates a read fault or corrupted frame.
+const float SENSOR_SANITY_LIMIT_MT = 500.0;
+
 // Final axis output range
 const float AXIS_LIMIT = 350.0;
 

firmware/src/controllers/MotionController.cpp

@@ -136,7 +136,7 @@ void MotionController::compute(const float raw[9], const float* baseline, float
     if (fabsf(y[i]) < dead) {
       // Below dead zone: decay Kalman estimate toward zero gradually.
       // Preserve covariance so the filter doesn't jitter at the boundary.
-      kalmanX_[i] *= 0.8f;
+      kalmanX_[i] *= Config::DEAD_DECAY_FACTOR;
       kalmanP_[i] = fminf(kalmanP_[i] + Config::KALMAN_Q * 0.1f, 1.0f);
     } else {
       kalmanStep(i, y[i]);

firmware/src/controllers/SensorController.cpp

@@ -76,7 +76,7 @@ bool SensorController::readRaw(float out[9]) {
   // Validate: reject frames where any axis reads exactly zero across all
   // components (likely I2C failure) or exceeds sane sensor range.
   for (int i = 0; i < 9; i++) {
-    if (fabsf(out[i]) > 500.0f) return false;  // Way outside EXTRA_SHORT_RANGE
+    if (fabsf(out[i]) > Config::SENSOR_SANITY_LIMIT_MT) return false;
   }
   // Check for dead sensor (all three axes exactly zero)
   for (int s = 0; s < 3; s++) {