fix S11 review: extract upsertPickedOverride, restore map_ on drag-cancel, clamp start to frames-1, pin startFrame>loopEnd wrap test

tests/test_sampler_core.cpp

@@ -592,6 +592,43 @@ static void testStartFrameWithLoop() {
     for (std::size_t i = 60; i < out.size(); ++i) CHECK(approx(out[i], 0.5, 1e-4));
 }
 
+static void testStartAfterLoopEndWrapsIntoLoop() {
+    // Regression (S11 reviewer finding): if startFrame > loop.end (but still < frameCount),
+    // the voice's initial read head is past the loop end. The wrap-while in renderFrame must
+    // pull it back into [loopStart, loopEnd) on the very first frame, so the note sounds from
+    // somewhere inside the loop rather than running off the sample end silently.
+    //
+    // Setup: 100-frame sample; loop is [20, 40); startFrame = 60 (past loop.end = 40).
+    // loop body is a constant 0.5 so every frame inside it reads 0.5.
+    // After wrap: readPos starts inside [20, 40), first output frame == 0.5.
+    // Voice must stay active (loop sustains it) and emit the loop value, NOT go silent.
+    SampleData s;
+    s.frames.resize(100, 0.0f);
+    for (int i = 20; i < 40; ++i) s.frames[i] = 0.5f;  // loop body
+    s.rootNote = 60;
+    s.startFrame = 60;  // > loop.end (40), < frameCount (100)
+    s.loop.hasLoop = true;
+    s.loop.start = 20;
+    s.loop.end   = 40;
+
+    Keymap km = Keymap::singleSampleChromatic(std::move(s));
+    VoiceEngine eng(1, km, flatAdsr());
+    eng.noteOn(60, 127);  // unity ratio, full velocity
+
+    std::vector<AudioSample> out;
+    eng.render(out, 50);
+
+    // Voice must still be active — the usable loop keeps it alive indefinitely.
+    CHECK(eng.activeVoiceCount() == 1);
+    // Every frame after the first wrap must read 0.5 (the loop body). We skip the very
+    // first frame because the fractional-position wrap lands somewhere in [20,40) and the
+    // exact offset depends on how many loop lengths fit into 60; what matters is that the
+    // voice is alive and emitting the loop value, not 0.0 (pre-loop region).
+    for (std::size_t i = 5; i < out.size(); ++i) {
+        CHECK(approx(out[i], 0.5, 1e-4));
+    }
+}
+
 // ---------------------------------------------------------------------------
 // velocity -> volume.
 // ---------------------------------------------------------------------------
@@ -656,6 +693,7 @@ int main() {
     testStartFrameZeroIsUnchanged();
     testStartFrameOutOfRangeClampsToZero();
     testStartFrameWithLoop();
+    testStartAfterLoopEndWrapsIntoLoop();
     testVelocityToVolume();
     testPolyphonyMixesAdditively();