fix: show empty timeline lanes when no video is loaded

Co-authored-by: Cursor <cursoragent@cursor.com>

src/lib/components/Timeline.svelte

@@ -83,7 +83,8 @@
       clipStore.selectedClipId,
       clipStore.pendingInPoint,
       waveformData,
-      session.thumbnailSpritesheets
+      session.thumbnailSpritesheets,
+      session.status === 'ready'
     );
     ctx.restore();
   }