refactor(studio): update layout, build config, and clean up exports

- NLELayout: add toolbar slot, composition breadcrumb, improved resizing
- App: update toolbar wiring, remove split/delete, add edit modal
- Remove AgentActivityTrack (unused)
- Update vite config with improved dev server and build settings
- Update package.json dependencies
- Simplify htmlEditor.ts (keep parseStyleString, mergeStyleIntoTag, findElementBlock)
- Update exports in index.ts

packages/studio/src/index.ts

@@ -27,6 +27,9 @@ export { FileTree } from "./components/editor/FileTree";
 // App
 export { StudioApp } from "./App";
 
+// Timeline toolbar
+export { TimelineToolbar } from "./components/timeline/TimelineToolbar";
+
 // Hooks
 export { useCodeEditor } from "./hooks/useCodeEditor";
 export type { OpenFile, UseCodeEditorReturn } from "./hooks/useCodeEditor";