fix: register cluster kv payloads

loadtest/im-pressure/histogram.go

@@ -10,6 +10,7 @@ var latencyBounds = []time.Duration{
 	time.Millisecond, 3 * time.Millisecond, 5 * time.Millisecond, 10 * time.Millisecond,
 	25 * time.Millisecond, 50 * time.Millisecond, 100 * time.Millisecond, 200 * time.Millisecond,
 	500 * time.Millisecond, time.Second, 2 * time.Second, 5 * time.Second, 10 * time.Second,
+	20 * time.Second, 30 * time.Second, 45 * time.Second, 60 * time.Second, 90 * time.Second, 120 * time.Second,
 }
 
 type DurationHistogram struct {

loadtest/im-pressure/merge_test.go

@@ -74,6 +74,23 @@ func TestMergedHistogramP95(t *testing.T) {
 	}
 }
 
+func TestMergedHistogramP95DoesNotUseMaximumForLongTail(t *testing.T) {
+	histogram := NewDurationHistogram()
+	for i := 0; i < 94; i++ {
+		histogram.Observe(5 * time.Second)
+	}
+	for i := 0; i < 5; i++ {
+		histogram.Observe(25 * time.Second)
+	}
+	histogram.Observe(70 * time.Second)
+	agents := []AgentSummary{{PublishCtrlLatency: histogram.Snapshot()}}
+	if got := mergedHistogramP95(agents, func(summary AgentSummary) HistogramSnapshot {
+		return summary.PublishCtrlLatency
+	}); got != 30000 {
+		t.Fatalf("p95=%v want=30000", got)
+	}
+}
+
 func TestMergedAckP95UsesExactAcceptedTimestamps(t *testing.T) {
 	base := time.Date(2026, 9, 27, 8, 0, 0, 0, time.UTC)
 	agents := []AgentSummary{{