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].

src/shell/instrument/reasampler_processor.h

@@ -394,9 +394,8 @@ private:
     // Both live_ and draining_ observe this same block — a block owned by a snapshot would
     // leave the drain's still-sounding voices deaf to the knob under them.
     instrument::engine::LiveParams liveParams_;
-    // The drawn-contour block, SampleData::liveContours' one target, under liveParams_' ordering
-    // constraint and for its reason. No automation merge: no contour is a host parameter, so both
-    // engines read the model/editor publish directly.
+    // SampleData::liveContours' one target, under liveParams_' ordering constraint above and for
+    // its reason (this directory's CLAUDE.md owns why it needs no automation merge).
     instrument::engine::LiveContourBlock liveContours_;
     // The block the ENGINE reads, and the ONE thing SampleData::live points at. Written only by
     // the audio thread, which merges liveParams_ with the host's automation points once per block