Drop Detector (Diagnostic de Chute)

// Détection d'anomalie par z-score
function detectDrop(current: number, baseline: number[], threshold = 2): {
  isDrop: boolean; zScore: number; changePct: number;
} {
  const mean = baseline.reduce((a, b) => a + b, 0) / baseline.length;
  const stddev = Math.sqrt(
    baseline.reduce((sum, v) => sum + (v - mean) ** 2, 0) / baseline.length
  );
  const zScore = stddev > 0 ? (current - mean) / stddev : 0;
  const changePct = mean > 0 ? ((current - mean) / mean) * 100 : 0;
  
  return { isDrop: zScore < -threshold, zScore, changePct };
}