fix: hide-exported checkbox state applied on session resume

_apply_playlist_filters now syncs _hide_exported from checkbox before
refreshing visibility, so exported files are hidden immediately on
startup without needing to toggle the checkbox.

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

main.py

@@ -2178,6 +2178,7 @@ class MainWindow(QMainWindow):
     def _apply_playlist_filters(self) -> None:
         """Apply profile-hidden files, export marks, and hide-exported filter."""
         self._refresh_playlist_checks()
+        self._playlist._hide_exported = self._chk_hide_exported.isChecked()
         self._playlist.set_hidden_basenames(self._db.get_hidden_files(self._profile))
 
     def _on_open_files(self) -> None: