fix(routing): show hydration shell on stack detail refresh

Avoid flashing HomeDashboard when activeView is editor but selectedFile
is not loaded yet on cold load or hard refresh.

frontend/src/components/EditorLayout.tsx

@@ -843,6 +843,8 @@ export default function EditorLayout() {
             onFleetActiveTabChange={setFleetActiveTab}
             renderEditor={renderEditor}
             stackUpdates={stackUpdates}
+            urlHydratingStack={urlHydratingStack}
+            isFileLoading={isFileLoading}
           />
         </div>
       );

frontend/src/components/EditorLayout/ViewRouter.tsx

@@ -16,6 +16,7 @@ import type { MuteRuleDraft } from '@/lib/muteRules';
 import type { ActiveView } from './hooks/useViewNavigationState';
 import type { StackUpdateInfo } from '@/types/imageUpdates';
 import type { SecurityTab, FleetTab } from '@/lib/events';
+import { isStackEditorDeepLink } from '@/lib/router/readUrlRouteState';
 
 // Paid-tier views are loaded on demand. Their internal PaidGate /
 // CapabilityGate wrappers render
@@ -101,6 +102,8 @@ export interface ViewRouterProps {
     // not on every parent render that lands on a different view.
     renderEditor: () => ReactNode;
     stackUpdates: Record<string, StackUpdateInfo>;
+    urlHydratingStack: string | null;
+    isFileLoading: boolean;
 }
 
 export function ViewRouter({
@@ -131,6 +134,8 @@ export function ViewRouter({
     onFleetActiveTabChange,
     renderEditor,
     stackUpdates,
+    urlHydratingStack,
+    isFileLoading,
 }: ViewRouterProps): ReactNode {
     const { can } = useAuth();
     if (activeView === 'settings') {
@@ -175,10 +180,14 @@ export function ViewRouter({
             </PaidGate>
         );
     }
-    // Fall-through: when activeView === 'editor' but selectedFile is
-    // null or the stack is still loading, drop through to the default
-    // HomeDashboard render below. This matches the pre-extraction
-    // behavior of the conditional ternary chain in EditorLayout.tsx.
+    // Stack editor deep link: keep a loading shell until selectedFile is set.
+    // Without this, cold load / refresh shows HomeDashboard while URL hydration runs.
+    if (activeView === 'editor' && !selectedFile) {
+        const awaitingStack = urlHydratingStack != null || isFileLoading || isStackEditorDeepLink();
+        if (awaitingStack) {
+            return <ViewSkeleton />;
+        }
+    }
     if (!isLoading && selectedFile && activeView === 'editor') {
         return renderEditor();
     }

frontend/src/lib/router/readUrlRouteState.ts

@@ -19,6 +19,13 @@ const DEFAULT: UrlRouteState = {
   filterNodeId: null,
 };
 
+/** True when the current URL is a stack editor deep link (cold-load bootstrap). */
+export function isStackEditorDeepLink(): boolean {
+  if (typeof window === 'undefined') return false;
+  const parsed = parsePath(window.location.pathname, window.location.search);
+  return parsed.view === 'editor' && parsed.stackName != null;
+}
+
 /** Read shell navigation fields from the current browser URL (cold-load bootstrap). */
 export function readUrlRouteState(): UrlRouteState {
   if (typeof window === 'undefined') return DEFAULT;