fix: tear down AG-UI subscription on RUN_FINISHED and RUN_ERROR

The bridge's next handler reacted to RUN_FINISHED / RUN_ERROR by
updating flowStore state but did not unsubscribe or resolve the
runFlowAGUI promise. Resolution relied on the AG-UI observable
completing after the terminal event, which holds only when the SSE
stream closes cleanly. A keepalive after RUN_FINISHED, a buffered chunk
the reader has not consumed, or a server that does not close eagerly
all leave the observable open. The canvas then stays on
isBuilding=true and running-status nodes never revert.

The fix mirrors the existing teardown in the error: and complete:
callbacks: call subscription.unsubscribe() + finish() on the terminal
event itself so resolution does not depend on the SSE stream closing.
Both branches updated symmetrically since RUN_FINISHED has the same
hang risk as RUN_ERROR.

No new test scaffold for this fix: reproducing the hang requires a
long-lived fake SSE response plus the real flowStore singleton (pulls
@xyflow/react and friends), and the fix surface is four lines mirroring
the documented complete: pattern. Evidence for the bug comes from the
PR #13307 code review and the step 6 code-review pass that re-surfaced
the same risk on the success branch. All 29 controllers/API/agui tests
still pass.

Author: ogabrielluiz

src/frontend/src/controllers/API/agui/run-flow-bridge.ts

@@ -144,12 +144,23 @@ export async function runFlowAGUI(opts: WorkflowRunOptions): Promise<void> {
           }
         } else if (event.type === EventType.RUN_FINISHED) {
           flowStore.setBuildInfo({ success: true });
+          // Tear the subscription down on the terminal event instead of
+          // waiting for `complete:` from the SSE stream. A server-side
+          // keepalive or buffered chunk after RUN_FINISHED can leave the
+          // observable open, which would leave the canvas stuck on
+          // ``isBuilding=true`` indefinitely.
+          subscription.unsubscribe();
+          finish();
         } else if (event.type === EventType.RUN_ERROR) {
           const message =
             (event as unknown as { message?: string }).message ??
             "Unknown run error";
           flowStore.setBuildInfo({ error: [message], success: false });
           setErrorData({ title: "Workflow run failed", list: [message] });
+          // Same teardown as RUN_FINISHED: a terminal error must not depend
+          // on the SSE stream closing on its own.
+          subscription.unsubscribe();
+          finish();
         }
       },
       error: (err: Error) => {