Merge ps-w8-t2-waveform: S11 waveform view + draggable loop points

src/vst/sampler_core.h

@@ -62,12 +62,19 @@ struct SampleData {
                                        // note-relative, so rate cancels for repitch)
     int rootNote = 60;                 // MIDI note recorded at (plays at unity here)
     SampleLoop loop;                   // sustain loop, if any
+    // Initial read position (frame offset) a voice starts playback at — frame 0 by
+    // default, so an unset start point is exactly the pre-S11 behavior. S11 makes this
+    // an instrument-side per-zone override (the "start point" marker); S15 builds on it
+    // (both play modes carry a modifiable start). Clamped into [0, frames) at note-on:
+    // a start >= the sample length is a no-op (voice starts at 0), never out of bounds.
+    std::int64_t startFrame = 0;
 
     // 2 iff a matching-length second channel exists; else 1. A framesR of a different
     // length than frames is treated as absent (mono) — a malformed pair never half-plays.
     int channelCount() const {
         return (!framesR.empty() && framesR.size() == frames.size()) ? 2 : 1;
     }
+
 };
 
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