fix: default Agent panel to collapsed

src/features/workbench/hooks/use-workbench-agent.ts

@@ -69,7 +69,7 @@ export function useWorkbenchAgent({
   const frontendActionEnabledRef = useRef(false);
   const onFrontendActionRef = useRef(onFrontendAction);
   const processedEnvelopeIdsRef = useRef(new Set<string>());
-  const [panelOpen, setPanelOpen] = useState(true);
+  const [panelOpen, setPanelOpen] = useState(false);
   const [panelCollapsing, setPanelCollapsing] = useState(false);
   const [mobileOpen, setMobileOpen] = useState(false);
   const [mobilePanelCollapsing, setMobilePanelCollapsing] = useState(false);