Unify UI workflows and streamline fleet management

src/lib/ui/stores/pipeline.ts

@@ -23,7 +23,7 @@ function updateDeployment(id: string, mutate: (d: PipelineDeployment) => void):
     });
 }
 
-export function startPipelineStream(): void {
+export function startPipelineStream(): (() => void) | undefined {
     if (!browser || source) return;
     source = new EventSource('/api/events/pipeline');
 
@@ -49,4 +49,5 @@ export function startPipelineStream(): void {
             d.servers.set(data.server, { state: data.state, players: data.players, error: data.error });
         });
     });
+    return () => { source?.close(); source = null; };
 }