Add benchmark fan duty cycle summary to report

audit/internal/platform/sat_fan_stress.go

@@ -426,6 +426,101 @@ func sampleFanSpeedsViaSensorsJSON() ([]FanReading, error) {
 	return fans, nil
 }
 
+// sampleFanDutyCyclePct reads fan PWM/duty-cycle controls from lm-sensors.
+// Returns the average duty cycle across all exposed PWM controls.
+func sampleFanDutyCyclePct() (float64, bool) {
+	out, err := exec.Command("sensors", "-j").Output()
+	if err != nil || len(out) == 0 {
+		return 0, false
+	}
+	return parseFanDutyCyclePctSensorsJSON(out)
+}
+
+func parseFanDutyCyclePctSensorsJSON(raw []byte) (float64, bool) {
+	var doc map[string]map[string]any
+	if err := json.Unmarshal(raw, &doc); err != nil {
+		return 0, false
+	}
+	var samples []float64
+	for _, features := range doc {
+		for name, feature := range features {
+			if strings.EqualFold(name, "Adapter") {
+				continue
+			}
+			featureMap, ok := feature.(map[string]any)
+			if !ok {
+				continue
+			}
+			if duty, ok := firstFanDutyValue(name, featureMap); ok {
+				samples = append(samples, duty)
+			}
+		}
+	}
+	if len(samples) == 0 {
+		return 0, false
+	}
+	return benchmarkMean(samples), true
+}
+
+func firstFanDutyValue(featureName string, feature map[string]any) (float64, bool) {
+	featureName = strings.ToLower(strings.TrimSpace(featureName))
+	if strings.Contains(featureName, "enable") || strings.Contains(featureName, "mode") || strings.Contains(featureName, "alarm") {
+		return 0, false
+	}
+	if strings.Contains(featureName, "pwm") {
+		for _, key := range []string{"input", "value", "current"} {
+			if value, ok := feature[key]; ok {
+				if duty, parsed := parseFanDutyValue(value); parsed {
+					return duty, true
+				}
+			}
+		}
+	}
+	keys := make([]string, 0, len(feature))
+	for key := range feature {
+		keys = append(keys, key)
+	}
+	sort.Strings(keys)
+	for _, key := range keys {
+		lower := strings.ToLower(key)
+		if !strings.Contains(lower, "pwm") {
+			continue
+		}
+		if strings.Contains(lower, "enable") || strings.Contains(lower, "mode") || strings.Contains(lower, "alarm") {
+			continue
+		}
+		if duty, parsed := parseFanDutyValue(feature[key]); parsed {
+			return duty, true
+		}
+	}
+	return 0, false
+}
+
+func parseFanDutyValue(value any) (float64, bool) {
+	switch v := value.(type) {
+	case float64:
+		return normalizePWMAsDutyPct(v)
+	case string:
+		if f, err := strconv.ParseFloat(strings.TrimSpace(v), 64); err == nil {
+			return normalizePWMAsDutyPct(f)
+		}
+	}
+	return 0, false
+}
+
+func normalizePWMAsDutyPct(raw float64) (float64, bool) {
+	if raw < 0 {
+		return 0, false
+	}
+	if raw <= 100 {
+		return raw, true
+	}
+	if raw <= 255 {
+		return raw / 255.0 * 100.0, true
+	}
+	return 0, false
+}
+
 func firstFanInputValue(feature map[string]any) (float64, bool) {
 	keys := make([]string, 0, len(feature))
 	for key := range feature {