feat: add bounded business state observability

internal/observability/metrics_test.go

@@ -112,6 +112,42 @@ func TestRuntimeObservationDoesNotExposeErrors(t *testing.T) {
 	disabled.RecordBatch("workflow", time.Now(), nil)
 	disabled.RecordDatabase(sql.DBStats{})
 }
+
+func TestBusinessSnapshotKeepsLastGoodStateOnFailure(t *testing.T) {
+	r := NewRegistry()
+	started := time.Now().Add(-25 * time.Millisecond)
+	r.RecordBusinessSnapshot(BusinessSnapshot{
+		TaskStates:               map[string]uint64{"WAITING": 3},
+		TaskOldestAgeSeconds:     12.5,
+		DeliveryStates:           map[string]uint64{"PENDING": 2},
+		DeliveryOldestAgeSeconds: 8.25,
+		WorkflowStates:           map[string]uint64{"RUNNING": 1},
+		WorkflowOldestAgeSeconds: 4.75,
+		Truncated:                true,
+	}, started, nil)
+	first := r.Render()
+	for _, want := range []string{
+		`orbit_pulse_tasks_state{state="WAITING"} 3`,
+		`orbit_result_deliveries_state{state="PENDING"} 2`,
+		`orbit_weave_workflows_state{state="RUNNING"} 1`,
+		"orbit_pulse_tasks_oldest_age_seconds 12.5",
+		"orbit_business_snapshot_truncated 1",
+		`orbit_business_snapshot_total{outcome="success"} 1`,
+	} {
+		if !strings.Contains(first, want) {
+			t.Fatalf("missing business sample %q", want)
+		}
+	}
+	lastSuccess := r.families["orbit_business_snapshot_last_success_timestamp_seconds"].series[""].value.Load()
+	r.RecordBusinessSnapshot(BusinessSnapshot{TaskStates: map[string]uint64{"WAITING": 99}}, time.Now(), context.DeadlineExceeded)
+	second := r.Render()
+	if !strings.Contains(second, `orbit_business_snapshot_total{outcome="timeout"} 1`) || !strings.Contains(second, `orbit_pulse_tasks_state{state="WAITING"} 3`) {
+		t.Fatal("failed sample overwrote good state")
+	}
+	if got := r.families["orbit_business_snapshot_last_success_timestamp_seconds"].series[""].value.Load(); got != lastSuccess {
+		t.Fatal("failed sample changed last success timestamp")
+	}
+}
 func TestHTTPBoundedLabelsAndPanicPreserved(t *testing.T) {
 	r := NewRegistry()
 	h := r.Middleware(http.HandlerFunc(func(w http.ResponseWriter, req *http.Request) { w.WriteHeader(202) }))