Fix EMA chasing spike during detection window

Freeze EMA updates when any spike candidate is detected (delta > threshold),
not just after stall is confirmed. This prevents EMA from rising to meet
the spike before the confirmation time elapses.

src/motor.cpp

@@ -347,13 +347,16 @@ void MotorController::checkStall() {
     // Calculate delta from average
     float delta = activeCurrent - _currentEMA;
     
-    // Update EMA (only when not in stall to prevent average rising during stall)
-    if (!_stalled) {
+    // Check if current spike exceeds delta threshold
+    bool spikeDetected = (delta > STALL_DELTA_THRESHOLD);
+    
+    // Update EMA only when no spike is being investigated
+    // This prevents EMA from "chasing" up to the spike during detection window
+    if (!spikeDetected && !_stalled) {
         _currentEMA = (STALL_EMA_ALPHA * activeCurrent) + ((1.0f - STALL_EMA_ALPHA) * _currentEMA);
     }
     
-    // Check if current spike exceeds delta threshold
-    if (delta > STALL_DELTA_THRESHOLD) {
+    if (spikeDetected) {
         if (_stallStartTime == 0) {
             // Start timing potential stall
             _stallStartTime = now;