instrument: latch the note done at the read-head run-off, fit the migrated fades, and lift the curve dial and overlay selection into pure modules

tests/test_sample_map.cpp

@@ -688,6 +688,28 @@ static void testResolvePlayRoundsAndFloorsNegatives() {
     CHECK(p.adsr.releaseFrames == 0);
 }
 
+// The retired Trigger fade pair was SOURCE frames; the AHD that replaced it stores wall-clock
+// seconds, and the codec's lift can only divide by the PROJECT rate. This is the far end of
+// that seam: the build multiplies by the DECODE rate, so a migrated fade comes back scaled by
+// decodeRate/projectRate whenever a file's own rate differs from the project's. The bound is
+// documented at the lift in component_state_io.h; this is its measured size.
+static void testMigratedFadeStretchesWhenTheDecodeRateDiffersFromTheProjectRate() {
+    PlaySeconds st;
+    st.trigAhd.attackSeconds = 441.0 / 44100.0;  // a 441-SOURCE-frame fade lifted at 44.1k
+    st.trigAhd.decaySeconds  = 882.0 / 44100.0;
+
+    // Matched rates are EXACT: the round trip through seconds loses nothing.
+    const PlayParams matched = resolvePlay(st, 44100);
+    CHECK(matched.trigAhd.attackFrames == 441);
+    CHECK(matched.trigAhd.decayFrames == 882);
+
+    // A 44.1 kHz file opened in a 48 kHz project: 441 * 48000/44100 = 480 source frames, ~8.8%
+    // longer than the fade the saved instance actually had.
+    const PlayParams stretched = resolvePlay(st, 48000);
+    CHECK(stretched.trigAhd.attackFrames == 480);
+    CHECK(stretched.trigAhd.decayFrames == 960);
+}
+
 // --- resolveCapture: the ONE override-beats-intrinsic fold ---------------------
 
 static SelectedSample ref(const std::string& rel, int root, bool hasLoop = false,
@@ -914,6 +936,7 @@ int main() {
     testResolvePlayConvertsWallClockAtTheRate();
     testResolvePlayCarriesTheFilterAndResolvesOnlyItsEnvelope();
     testResolvePlayRoundsAndFloorsNegatives();
+    testMigratedFadeStretchesWhenTheDecodeRateDiffersFromTheProjectRate();
     testResolveCaptureUsesIntrinsicsWhenNoOverride();
     testResolveCaptureOverridesBeatIntrinsics();
     testResolveCaptureLoopOverrideCanDisableTheLoop();