80011274f2
- Add routing_mode (mono/4cm) and routing_breakpoint (default 7) to Preset - Serialize/deserialize in _preset_to_dict / _preset_from_dict - Backward compatible — old presets default to mono/7 - Add get_4cm_config() / set_4cm_config() helpers on PresetManager - set_4cm_config validates mode and saves back to disk - All 48 related tests pass (46 preset + 2 integration activation)