fix: defer playlist scroll restore to next event loop iteration

Qt processes layout changes asynchronously, so restoring the scrollbar
immediately after _after_load was too early. Use QTimer.singleShot(0)
to restore after Qt finishes processing pending layout events.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

main.py

@@ -2246,10 +2246,9 @@ class MainWindow(QMainWindow):
         self._spn_spread.setValue(float(self._settings.value("spread", "3.0")))
         self._preview_win.show()
         self._preview_timer.start()
-        # Restore playlist scroll that video load disturbed.
-        sb = self._playlist.verticalScrollBar()
-        if sb and hasattr(self, '_playlist_scroll_stash'):
-            sb.setValue(self._playlist_scroll_stash)
+        # Restore playlist scroll after Qt processes pending layout events.
+        if hasattr(self, '_playlist_scroll_stash'):
+            QTimer.singleShot(0, self._restore_playlist_scroll)
 
         # Run DB fuzzy match off the main thread — can be slow on large databases.
         filename = os.path.basename(self._file_path)
@@ -2267,6 +2266,11 @@ class MainWindow(QMainWindow):
             self.statusBar().clearMessage()
         self._timeline.set_markers(markers)
 
+    def _restore_playlist_scroll(self) -> None:
+        sb = self._playlist.verticalScrollBar()
+        if sb:
+            sb.setValue(self._playlist_scroll_stash)
+
     def _refresh_markers(self) -> None:
         filename = os.path.basename(self._file_path)
         markers = self._db.get_markers(filename, self._profile)