feat: add system sound alert module

Made-with: Cursor

tests/test_sound.py

@@ -0,0 +1,20 @@
+import pytest
+from unittest.mock import patch, MagicMock
+from cursor_flasher.sound import play_alert
+from cursor_flasher.config import Config
+
+
+class TestPlayAlert:
+    def test_does_nothing_when_disabled(self):
+        config = Config(sound_enabled=False)
+        play_alert(config)
+
+    @patch("cursor_flasher.sound.NSSound")
+    def test_plays_named_sound(self, mock_nssound):
+        mock_sound_obj = MagicMock()
+        mock_nssound.soundNamed_.return_value = mock_sound_obj
+        config = Config(sound_enabled=True, sound_name="Glass", sound_volume=0.7)
+        play_alert(config)
+        mock_nssound.soundNamed_.assert_called_once_with("Glass")
+        mock_sound_obj.setVolume_.assert_called_once_with(0.7)
+        mock_sound_obj.play.assert_called_once()