instrument: deliver continuous playback params live to sounding voices via a seqlock block, holding normalized stage position across time edits

src/shell/instrument/editor_session.cpp

@@ -136,6 +136,23 @@ void ReaSamplerEditor::commitAndReload() {
 #endif
 }
 
+void ReaSamplerEditor::commitLive() {
+    // UI thread only. See the declaration for why this still writes the parameter set.
+    if (!processor_) return;
+    processor_->setInstrumentParams(params_);
+    processor_->publishLiveParams();
+}
+
+bool ReaSamplerEditor::dragCommitsLive(DragKind kind, int paramId) const {
+    if (kind == DragKind::kDeckKnob) {
+        // Negative ids are the processor-side sentinels (preview velocity), not parameter-set
+        // controls, so they never reach the enum.
+        return paramId >= 0 &&
+               instrument::ui::isLiveDeckParam(static_cast<ParamControl>(paramId));
+    }
+    return kind == DragKind::kEnvNode && params_.play.playMode == PlayMode::Gate;
+}
+
 void ReaSamplerEditor::loadSelection(const std::string& id) {
     // A load REPLACES the loaded sound. The shaping parameters (play mode, envelopes, pitch
     // engine, key-track, velocity curve) are NOT reset — the one set governs whatever is