S15/S16: Gate(AHDSR)/Trigger play modes + Varispeed/Preserve pitch engines + AD pitch envelope

Per-zone play params on SampleData; hand-rolled pure pitch_shift OLA for Preserve (WDL drags
windows.h); zone-payload v3 tail; RT-safe pre-warmed shifters + Preserve voice cap.

src/vst/reasampler_processor.h

@@ -51,8 +51,11 @@ struct LoadedInstrument {
     std::uint64_t installedAt = 0;  // reload generation at which this was installed
 
     LoadedInstrument(Keymap km, std::size_t maxVoices, const AdsrParams& adsr,
-                     std::uint64_t gen)
-        : keymap(std::move(km)), engine(maxVoices, keymap, adsr), installedAt(gen) {}
+                     std::uint64_t gen, std::size_t preserveVoiceCap = 0,
+                     std::int64_t preserveWindowFrames = 0)
+        : keymap(std::move(km)),
+          engine(maxVoices, keymap, adsr, preserveVoiceCap, preserveWindowFrames),
+          installedAt(gen) {}
 
     LoadedInstrument(const LoadedInstrument&) = delete;
     LoadedInstrument& operator=(const LoadedInstrument&) = delete;