Make spline EG drags audible live: held and new notes follow a dragged knot

Contours ride their own seqlock block into a double-buffered engine copy, and the swap step is smoothed. Each drag move publishes contours without a model write; release still commits and reloads.

src/shell/instrument/reasampler_editor.h

@@ -267,6 +267,12 @@ private:
     // the knob. Does not repaint; callers already do. UI thread only.
     void commitLive();
 
+    // The drawn-contour drag's per-move publish: params_' three contours straight to the voices,
+    // with NO parameter-set write — why is this directory's CLAUDE.md (the contour-drag note
+    // under the commit tiers). Every path that ends such a drag without its release's
+    // commitAndReload — capture-lost — must call this again after restoring params_. UI thread.
+    void publishContoursLive();
+
     // Whether an in-flight drag commits live rather than through a reload. A deck knob is
     // live per deckParamCommit; an envelope-node drag is live in EITHER mode — see
     // liveCommitFor (deck_groups.h) for why.