fix(mock): seed docker host disk and network I/O history

Seeded mock history recorded docker hosts with cpu, memory and disk only,
while the synthetic generator used past the seed window emits the full guest
metric set. The result was an inversion across chart ranges: a docker host had
no diskread, diskwrite, netin or netout history at 5m through 24h and full
history at 7d and 30d. Real docker hosts report both through the agent, so the
seed now covers the same series the generator does and every range agrees.

The guardrail test asserts seeded coverage matches the synthetic metric set
rather than a hand-listed set, so a future series added to one path cannot
quietly skip the other.

docs/release-control/v6/internal/subsystems/monitoring.md

@@ -496,7 +496,13 @@ changes.
    fixture registries synced in `internal/mock/metric_personas.go`, never a
    per-call fixture graph clone on the chart path. A percentage series without
    its byte companion silently empties the host-capacity memory column instead
-   of degrading it.
+   of degrading it. The same obligation is general. Seeded coverage in
+   `internal/monitoring/mock_metrics_history.go` and the synthetic generator
+   must carry the same series set per resource kind, so a chart window never
+   decides whether a series exists. Docker hosts seed disk and network I/O for
+   that reason, matching what the agent reports on a real host. A series
+   present on one range and absent on another reads as a broken column, not as
+   missing history.
    Discovery config and configured-host IP resolution must stay off the
    monitor lock. `internal/monitoring/monitor_discovery_helpers.go` exposes
    the canonical `discoveryConfigSnapshot()` that discovery providers consume,

internal/monitoring/mock_metrics_history.go

@@ -914,13 +914,16 @@ func seedMockMetricsHistory(mh *MetricsHistory, ms *metrics.Store, graph mock.Fi
 			continue
 		}
 
+		// Docker hosts report disk and network I/O through the agent, and the
+		// synthetic generator emits both beyond the seeded window. Seeding the
+		// same series keeps short ranges from being the only ones missing them.
 		recordGuest(
 			[]string{"dockerHost:" + host.ID},
 			"dockerHost",
 			host.ID,
 			true,
-			false,
-			false,
+			true,
+			true,
 		)
 
 		for _, container := range host.Containers {

internal/monitoring/mock_metrics_history_test.go

@@ -1989,3 +1989,29 @@ func TestSeedMockMetricsHistory_DiskTelemetryParityAcrossNativeAndTrueNAS(t *tes
 		}
 	}
 }
+
+// Seeded mock history and the synthetic generator must agree on which series a
+// resource carries. Docker hosts previously seeded cpu, memory, and disk only,
+// so their I/O series existed on ranges past the seed window and nowhere else.
+func TestMockDockerHostSeedCoversTheSameSeriesAsTheSyntheticGenerator(t *testing.T) {
+	previous := mock.IsMockEnabled()
+	mustSetMockEnabled(t, true)
+	defer mustSetMockEnabled(t, previous)
+
+	history := NewMetricsHistory(4096, 24*time.Hour)
+	graph := mock.CurrentFixtureGraph()
+	if len(graph.State.DockerHosts) == 0 {
+		t.Fatal("mock fixture graph has no docker hosts")
+	}
+
+	now := time.Now().UTC()
+	seedMockMetricsHistory(history, nil, graph, now, 2*time.Hour, time.Minute)
+
+	hostID := graph.State.DockerHosts[0].ID
+	for _, metricType := range mockGuestChartMetricTypes {
+		points := history.GetGuestMetrics("dockerHost:"+hostID, metricType, 2*time.Hour)
+		if len(points) == 0 {
+			t.Fatalf("seeded docker host %s is missing the %s series", hostID, metricType)
+		}
+	}
+}