Service both VST3 parameter channels, and promote pitch key-track and Trigger length so all 44 ids issue

The SDK's own single-component sample drains inputParameterChanges in
process() and implements setParamNormalized; automation was reading the
GUI channel alone. The audio thread now patches a block it solely owns.

src/core/instrument/engine/live_params.cpp

@@ -5,8 +5,13 @@
 
 namespace reasampler::instrument::engine {
 
-LiveValues foldLive(const PlayParams& params) {
+LiveValues foldLive(const PlayParams& params, double keyTrack) {
     LiveValues v;
+    v.keyTrack = keyTrack;
+    // Folded here, not at the voice: Voice::start reads the block's value directly, so the
+    // spline rule has to be applied on the way in or the two would answer differently.
+    v.splineActive = splineActive(params);
+    v.lengthFraction = effectiveLengthFraction(params);
     v.filterSettings = params.filter.settings;
     v.filterModAmount = params.filter.modAmount;
     v.filterVelAmount = params.filter.velAmount;