fix(metrics): stabilize cpu and power sampling

audit/internal/webui/server_test.go

@@ -89,6 +89,19 @@ func TestChartDataFromSamplesUsesFullHistory(t *testing.T) {
 	}
 }
 
+func TestNormalizePowerSeriesHoldsLastPositive(t *testing.T) {
+	got := normalizePowerSeries([]float64{0, 480, 0, 0, 510, 0})
+	want := []float64{0, 480, 480, 480, 510, 510}
+	if len(got) != len(want) {
+		t.Fatalf("len=%d want %d", len(got), len(want))
+	}
+	for i := range want {
+		if got[i] != want[i] {
+			t.Fatalf("got[%d]=%v want %v", i, got[i], want[i])
+		}
+	}
+}
+
 func TestRootRendersDashboard(t *testing.T) {
 	dir := t.TempDir()
 	path := filepath.Join(dir, "audit.json")