fix: replace MetadataEvent double cast with proper EventStreamMetadataEvent type

The broadcaster produces a simpler shape than the workspace-migration
MetadataEvent discriminated union, and includes updatedCollectionHash
which MetadataEvent lacks. Define EventStreamMetadataEvent to match
what the broadcaster actually produces, removing the as unknown as cast.

https://claude.ai/code/session_01EcJHCeJy44AKw2rafgQcnu

packages/twenty-server/src/engine/subscriptions/types/event-stream-payload.type.ts

@@ -1,10 +1,22 @@
 import { type ObjectRecordSubscriptionEvent } from 'src/engine/subscriptions/types/object-record-subscription-event.type';
-import { type MetadataEvent } from 'src/engine/workspace-manager/workspace-migration/workspace-migration-runner/types/metadata-event';
+
+export type EventStreamMetadataEvent = {
+  metadataName: string;
+  type: 'created' | 'updated' | 'deleted';
+  recordId: string;
+  properties: {
+    updatedFields?: string[];
+    before?: Record<string, unknown>;
+    after?: Record<string, unknown>;
+    diff?: Record<string, unknown>;
+  };
+  updatedCollectionHash?: string;
+};
 
 export type EventStreamPayload = {
   objectRecordEventsWithQueryIds: {
     queryIds: string[];
     objectRecordEvent: ObjectRecordSubscriptionEvent;
   }[];
-  metadataEvents: MetadataEvent[];
+  metadataEvents: EventStreamMetadataEvent[];
 };

packages/twenty-server/src/engine/subscriptions/workspace-event-broadcaster/workspace-event-broadcaster.service.ts

@@ -49,7 +49,7 @@ export class WorkspaceEventBroadcaster {
         recordId: event.recordId,
         properties: event.properties,
         updatedCollectionHash,
-      })) as unknown as EventStreamPayload['metadataEvents'],
+      })),
     };
 
     for (const [streamChannelId, streamData] of streamsData) {