✅ | Boost coverage to 60% with 256 passing tests

- mpris.py: 81% → 100% — import fallbacks, flush_props edge cases,
  stop_async error path, run_async exception path, notify loops
- player.py: 51% → 73% — AudioPlayer state/volume/loop/queue tests,
  _on_download_failed, _on_download_succeeded, _on_playback_state,
  _on_media_status, seek/skip/previous, _start_prefetch, _advance,
  _cancel_active_downloads, DownloadWorker._do_cancel
- test_gui_widgets.py: 50 → 88 tests across TestAudioPlayer and
  existing widget tests
- 5 modules at 100%: config, discord_rpc, main, mpris, music_db

tests/test_import_fallbacks.py

@@ -193,6 +193,29 @@ class TestPlayerQtFallback:
             assert player.QMediaPlayer is not None
             assert hasattr(player.QMediaPlayer, "PlaybackState")
 
+    def test_stub_qmediaplayer_methods(self):
+        """Stub QMediaPlayer methods can be called without error."""
+        _clean_pyside_modules()
+        side_effect = _make_importer(block_pyside=True)
+
+        with mock.patch("builtins.__import__", side_effect=side_effect):
+            import player
+
+            mp = player.QMediaPlayer()
+            # Methods that should be no-ops
+            mp.set_source("https://example.com/audio.mp3")
+            mp.play()
+            mp.pause()
+            mp.stop()
+            mp.set_position(30000)
+            mp.set_audio_output(None)
+
+            # Methods that return values
+            assert mp.position() == 0
+            assert mp.duration() == 0
+            assert mp.get_playback_state() == 0  # stopped_state
+            assert mp.get_audio_output() is None
+
 
 # ═══════════════════════════════════════════════════════════════════════════════
 # gui.py fallback