fix(frontend/builder): auto-apply AI graph actions after each streaming turn

handleApplyAction was defined and exported but never called, so the
"AI applied these changes" panel was displaying actions that had no
effect. Wire up a handleApplyActionRef so the status-change effect
can safely apply each parsed action to the local Zustand stores once
per completed AI turn, before the canvas refetch resolves.

autogpt_platform/frontend/src/app/(platform)/build/components/BuilderChatPanel/useBuilderChatPanel.ts

@@ -35,6 +35,9 @@ export function useBuilderChatPanel({
   // Guards whether the seed message has been sent for this session.
   const hasSentSeedMessageRef = useRef(false);
   const sendMessageRef = useRef<SendMessageFn | null>(null);
+  const handleApplyActionRef = useRef<((action: GraphAction) => void) | null>(
+    null,
+  );
   const prevStatusRef = useRef<string>("ready");
 
   const [{ flowID }] = useQueryStates({ flowID: parseAsString });
@@ -122,6 +125,7 @@ export function useBuilderChatPanel({
   // Keep a stable ref so the initialization effect can call sendMessage
   // without including it in the deps array (avoids re-triggering the effect).
   sendMessageRef.current = sendMessage;
+  handleApplyActionRef.current = handleApplyAction;
 
   // Parsed actions from the last assistant message. Gated on `status ===
   // "ready"` so the expensive regex parse only runs once per completed AI turn,
@@ -142,23 +146,25 @@ export function useBuilderChatPanel({
     });
   }, [messages, status]);
 
-  // Refresh the canvas only when the AI turn actually mutated the graph via
-  // edit_agent. Gating on parsedActions.length > 0 avoids an unnecessary
-  // refetch after read-only turns (e.g. the initial description response).
+  // After each AI turn: apply parsed actions to the local graph and refresh
+  // the canvas from the server. Gating on parsedActions.length > 0 avoids an
+  // unnecessary refetch after read-only turns (e.g. the initial description).
   useEffect(() => {
     const prev = prevStatusRef.current;
     prevStatusRef.current = status;
     if (
       status === "ready" &&
       (prev === "streaming" || prev === "submitted") &&
-      flowID &&
       parsedActions.length > 0
     ) {
-      queryClient.invalidateQueries({
-        queryKey: getGetV1GetSpecificGraphQueryKey(flowID),
-      });
+      parsedActions.forEach((a) => handleApplyActionRef.current?.(a));
+      if (flowID) {
+        queryClient.invalidateQueries({
+          queryKey: getGetV1GetSpecificGraphQueryKey(flowID),
+        });
+      }
     }
-  }, [status, flowID, queryClient, parsedActions.length]);
+  }, [status, flowID, queryClient, parsedActions]);
 
   // Send the seed message once per session. `nodes` and `edges` are included in
   // the dep array so this effect always has fresh data; the hasSentSeedMessageRef