feat(audio): add a family dictation tone picker (#707)

Settings → Audio can pick start/stop cues from the shared catalog
(lift, flick, ember, step, voca, soft, chirp, scale, drop, glass, off).
New installs and any missing or unknown sound_effects.tone value use
voca. A saved id, including off, is left alone.

The old start_recording/stop_recording files stay on disk. They are
no longer the implicit default. Error cues still follow the existing
enable switch.

tests/test_config_manager.py

@@ -485,6 +485,15 @@ class TestConfigManager(unittest.TestCase):
         config_manager = ConfigManager()
         self.assertTrue(config_manager.is_sound_effects_enabled())
 
+    def test_sound_effects_tone_defaults_to_voca(self):
+        """New installs and missing tone keys resolve to voca."""
+        from vocalinux.ui.config_manager import DEFAULT_SOUND_EFFECT_TONE
+
+        config_manager = ConfigManager()
+        self.assertEqual(DEFAULT_SOUND_EFFECT_TONE, "voca")
+        self.assertEqual(config_manager.get_sound_effects_tone(), "voca")
+        self.assertEqual(config_manager.config["sound_effects"]["tone"], "voca")
+
     def test_missing_tray_warning_enabled_by_default(self):
         """Test that the missing tray support warning is enabled by default."""
         config_manager = ConfigManager()