Update flow diagrams for event bus architecture, cancel cleanup, and SubscribeEvents

Ultraworked with [Sisyphus](https://github.com/code-yeongyu/claude-agent)

Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>

docs/architecture/flows/monitor-album-stream-already-owned.puml

@@ -5,9 +5,16 @@ title MonitorAlbumStream: Already Owned Handling
 
 actor Client
 participant "monitorWorkflow" as Workflow
+participant "EventBus" as Bus
 database "PostgreSQL" as DB
 participant "IndexerService" as Indexer
 
+note over Client, Indexer #lightblue
+All events are persisted to album_events table (DB first)
+then published to EventBus for live subscribers.
+In automatic mode, workflow runs as background goroutine.
+end note
+
 == Scenario A: Automatic Mode - Early Return ==
 
 Client -> Workflow: StartMonitorRequest(mode=AUTOMATIC)