feat: observe workflow inbox backlog

internal/observability/business.go

@@ -21,6 +21,10 @@ type BusinessSnapshot struct {
 	WorkflowStates map[string]uint64
 	// WorkflowOldestAgeSeconds 未终结流程中最早更新时间的年龄。
 	WorkflowOldestAgeSeconds float64
+	// InboxStates Weave 内部事件状态的有界计数。
+	InboxStates map[string]uint64
+	// InboxOldestAgeSeconds 待消费内部事件中最早可处理记录的年龄。
+	InboxOldestAgeSeconds float64
 	// Truncated 是否至少有一类状态达到采样上限。
 	Truncated bool
 	// RecentEvents 固定事件类别在最近窗口内的有界数量。
@@ -63,6 +67,9 @@ func (r *Registry) RecordBusinessSnapshot(snapshot BusinessSnapshot, started tim
 	for _, state := range workflowStates {
 		r.SetGauge("orbit_weave_workflows_state", float64(snapshot.WorkflowStates[state]), Labels{"state": state})
 	}
+	for _, state := range inboxStates {
+		r.SetGauge("orbit_weave_inbox_state", float64(snapshot.InboxStates[state]), Labels{"state": state})
+	}
 	for _, eventType := range eventTypes {
 		r.SetGauge("orbit_business_events_recent", float64(snapshot.RecentEvents[eventType]), Labels{"event": eventType})
 	}
@@ -73,6 +80,7 @@ func (r *Registry) RecordBusinessSnapshot(snapshot BusinessSnapshot, started tim
 	r.SetGauge("orbit_pulse_tasks_oldest_age_seconds", snapshot.TaskOldestAgeSeconds, nil)
 	r.SetGauge("orbit_result_delivery_oldest_age_seconds", snapshot.DeliveryOldestAgeSeconds, nil)
 	r.SetGauge("orbit_weave_workflow_oldest_age_seconds", snapshot.WorkflowOldestAgeSeconds, nil)
+	r.SetGauge("orbit_weave_inbox_oldest_age_seconds", snapshot.InboxOldestAgeSeconds, nil)
 	truncated := 0.0
 	if snapshot.Truncated {
 		truncated = 1