Fix spline-drag rollback, bake contour leak, held-note live miss, amp clamp

Editor close mid-drag now rolls back published contours like capture-loss does; bake detaches liveContours so a printed capture can't observe a live drag; a held note now receives a live publish that lands in the same block as a note-on; amp spline read clamped to [0,1].

tests/test_bake_render.cpp

@@ -11,6 +11,7 @@
 #include "../src/core/instrument/bake/bake_render.h"
 
 #include "../src/core/instrument/engine/limiter.h"
+#include "../src/core/instrument/engine/live_contours.h"
 #include "../src/core/instrument/engine/live_params.h"
 
 #include <cmath>
@@ -338,6 +339,36 @@ int main() {
         CHECK(sameSamples(audio, reference));
     }
 
+    // --- The bake detaches liveContours too, not just live -------------------------------
+    // A contour drag in flight publishes into liveContours (see reasampler_processor.h); a
+    // render that observed it would print whatever the user happens to be dragging instead
+    // of the dialed shape already sitting in play.ampSpline.contour.
+    {
+        instrument::engine::LiveContourBlock block;
+        SampleData s = makeSample(/*stereo=*/false, /*frames=*/1000);
+        s.play.playMode = PlayMode::Trigger;
+        s.play.ampSpline.mode = EnvMode::Spline;
+        s.play.ampSpline.contour = instrument::engine::VelocityCurve::flat();  // dialed: unity
+
+        // Publish a very different contour — ramping down to silence — into the block.
+        s.liveContours = &block;
+        {
+            PlayParams dragged = s.play;
+            dragged.ampSpline.contour = instrument::engine::VelocityCurve::rampDown();
+            block.publish(instrument::engine::foldContours(dragged));
+        }
+
+        const BakePlan plan = planOf(/*total=*/1000, /*noteOn=*/0, /*noteOff=*/1000);
+        const BakeAudio audio = renderBake(s, plan, kUnity, kNoLimiter);
+
+        CHECK(s.liveContours == &block);  // the caller's own snapshot was not detached
+
+        SampleData detached = s;
+        detached.liveContours = nullptr;
+        const BakeAudio reference = renderBake(detached, plan, kUnity, kNoLimiter);
+        CHECK(sameSamples(audio, reference));
+    }
+
     // --- Regression baseline: the neutral render is the source, sample for sample --------
     // A Trigger voice at its own root under Varispeed reads at ratio exactly 1 and hits no
     // filter, so every printed frame equals its source frame PROVIDED the amp curve's gain at