fix(studio): prevent composition switch loop on sub-composition navigation (#754)

Circular state update between activeCompPath and compositionStack caused
the preview to flicker when navigating to sub-compositions and scrubbing.
The cycle: activeCompPath change → useEffect updates compositionStack →
onCompositionChange fires → setActiveCompPath + refreshPreviewDocumentVersion
→ re-render → effect re-evaluates → repeat. Fixed by guarding both sides:
onCompositionChange skips if path unchanged, updateCompositionStack skips
notification if top-of-stack ID unchanged.

Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

packages/studio/src/components/StudioPreviewArea.tsx

@@ -108,8 +108,12 @@ export function StudioPreviewArea({
         onCompositionChange={(compPath) => {
           // Sync activeCompPath when user drills down via timeline double-click
           // or navigates back via breadcrumb — keeps sidebar + thumbnails in sync.
-          setActiveCompPath(compPath);
-          refreshPreviewDocumentVersion();
+          // Guard against no-op updates to prevent circular refresh cascades
+          // between activeCompPath → compositionStack → onCompositionChange.
+          if (compPath !== activeCompPath) {
+            setActiveCompPath(compPath);
+            refreshPreviewDocumentVersion();
+          }
         }}
         onIframeRef={handlePreviewIframeRef}
         previewOverlay={

packages/studio/src/components/nle/NLELayout.tsx

@@ -203,8 +203,11 @@ export const NLELayout = memo(function NLELayout({
   const updateCompositionStack: typeof setCompositionStack = useCallback((action) => {
     setCompositionStack((prev) => {
       const next = typeof action === "function" ? action(prev) : action;
-      const id = next[next.length - 1]?.id;
-      queueMicrotask(() => onCompositionChangeRef.current?.(id === "master" ? null : id));
+      const prevId = prev[prev.length - 1]?.id;
+      const nextId = next[next.length - 1]?.id;
+      if (prevId !== nextId) {
+        queueMicrotask(() => onCompositionChangeRef.current?.(nextId === "master" ? null : nextId));
+      }
       return next;
     });
   }, []);