Add Oscillator::setParams() which updates detune, pan, and gain for
already-initialised sub-voices without resetting their phases. This
preserves phase continuity when unison or spread is LFO-modulated at
control rate. noteOn() now just seeds phases and delegates to
setParams().
Precompute panL/panR in SubVoice instead of calling cos/sin per
sample. Add paramsValid and cachedParams to skip redundant work.
Replace SynthVoice's lastUnisonA/B tracking with a single
oscillatorsNeedNoteOn flag: noteOn sets it, render clears it after
the first block. Add SubLevel and NoiseLevel to the per-voice
modulation targets so they can be modulated like other parameters.
biggy