fix: default streamSubgraphs to true in LangGraph agent wrapper

The @ag-ui/langgraph 0.0.31+ changed the default for streamSubgraphs
from true to undefined, breaking subagent streaming. This enriches the
run() input's forwardedProps with streamSubgraphs: true as a default,
while preserving any explicit user override via the nullish coalescing
operator.

Author: jpr5

packages/runtime/src/lib/runtime/agent-integrations/langgraph/agent.ts

@@ -154,7 +154,14 @@ export class LangGraphAgent extends AGUILangGraphAgent {
 
   // @ts-ignore
   run(input: RunAgentInput): Observable<BaseEvent> {
-    return super.run(input).pipe(
+    const enrichedInput = {
+      ...input,
+      forwardedProps: {
+        ...input.forwardedProps,
+        streamSubgraphs: input.forwardedProps?.streamSubgraphs ?? true,
+      },
+    };
+    return super.run(enrichedInput).pipe(
       map((processedEvent) => {
         // Turn raw event into emit state snapshot from tool call event
         if (processedEvent.type === EventType.RAW) {