(fix)workflow: stable outside-click handler, drop trailing whitespace

Address Copilot review on #2600:
- pass a useCallback handler to useOutsideAlerter so the global mousedown
  listener isn't torn down/re-added on every WorkflowBuilder render
- remove trailing spaces after {displayName} in AgentPageHeader

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

frontend/src/agents/AgentPageHeader.tsx

@@ -91,7 +91,7 @@ export default function AgentPageHeader({
           <BreadcrumbItem>
             {currentPage === 'overview' ? (
               <BreadcrumbPage title={displayName} className="w-[16ch] truncate">
-                {displayName}              
+                {displayName}
               </BreadcrumbPage>
             ) : (
               <BreadcrumbLink asChild>

frontend/src/agents/workflow/WorkflowBuilder.tsx

@@ -781,11 +781,13 @@ function WorkflowBuilderInner() {
     setShowWorkflowSettings(false);
   }, []);
 
+  const handleCloseWorkflowSettings = useCallback(() => {
+    setShowWorkflowSettings(false);
+  }, []);
+
   useOutsideAlerter(
     workflowSettingsRef,
-    () => {
-      setShowWorkflowSettings(false);
-    },
+    handleCloseWorkflowSettings,
     [],
     false,
   );