- Add AdditiveEngine (48 params) and FMEngine (55 params) wrapping FaustEngineBase
- Remove comingSoon flags from ENGINES descriptors
- Replace stub onSwitch handler with real engine construction + init + setActiveEngine
- Fix setActiveEngine EOC rewire to work with both C15 (_bridge.audioContext) and Faust (_audioCtx)
- Fix _startEocChain audioCtx resolution to support Faust engines
- Fix synth param send loop: use N_OUTPUTS instead of hardcoded SYNTH_PARAM_MAP.length