Fix InstancedNode losing InstanceNodeControl after deserialization (#2605)

* Initial plan

* Fix InstancedNode deserialization - add write/read methods to preserve control

Co-authored-by: riccardobl <4943530+riccardobl@users.noreply.github.com>

* Simplify test to avoid asset dependencies - all tests passing

Co-authored-by: riccardobl <4943530+riccardobl@users.noreply.github.com>

* Address code review feedback - remove redundant test

Co-authored-by: riccardobl <4943530+riccardobl@users.noreply.github.com>

---------

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: riccardobl <4943530+riccardobl@users.noreply.github.com>

Author: Copilot

jme3-core/src/main/java/com/jme3/scene/instancing/InstancedNode.java

@@ -407,4 +407,16 @@ public void onMeshChange(Geometry geom) {
     public void onGeometryUnassociated(Geometry geom) {
         removeFromInstancedGeometry(geom);
     }
+
+    @Override
+    public void write(JmeExporter ex) throws IOException {
+        super.write(ex);
+        ex.getCapsule(this).write(control, "control", null);
+    }
+
+    @Override
+    public void read(JmeImporter im) throws IOException {
+        super.read(im);
+        control = (InstancedNodeControl) im.getCapsule(this).readSavable("control", null);
+    }
 }

jme3-core/src/test/java/com/jme3/scene/instancing/InstancedNodeTest.java

@@ -0,0 +1,72 @@
+/*
+ * Copyright (c) 2025 jMonkeyEngine
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ * * Redistributions of source code must retain the above copyright
+ *   notice, this list of conditions and the following disclaimer.
+ *
+ * * Redistributions in binary form must reproduce the above copyright
+ *   notice, this list of conditions and the following disclaimer in the
+ *   documentation and/or other materials provided with the distribution.
+ *
+ * * Neither the name of 'jMonkeyEngine' nor the names of its contributors
+ *   may be used to endorse or promote products derived from this software
+ *   without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
+ * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
+ * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
+ * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
+ * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
+ * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
+ * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
+ * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+ * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+package com.jme3.scene.instancing;
+
+import com.jme3.asset.AssetManager;
+import com.jme3.asset.DesktopAssetManager;
+import com.jme3.export.binary.BinaryExporter;
+import org.junit.Assert;
+import org.junit.Test;
+
+/**
+ * Verifies that the {@link InstancedNode} class works correctly.
+ *
+ * @author copilot
+ */
+public class InstancedNodeTest {
+
+    private static final AssetManager assetManager = new DesktopAssetManager();
+
+    /**
+     * Test that InstancedNode serialization preserves the InstanceNodeControl.
+     */
+    @Test
+    public void testSerializationPreservesControl() throws Exception {
+        // Create an InstancedNode
+        InstancedNode instancedNode = new InstancedNode("test_instanced_node");
+
+        // Verify the control exists before serialization
+        Assert.assertEquals("InstancedNode should have 1 control before serialization", 
+                            1, instancedNode.getNumControls());
+
+        // Serialize and deserialize
+        InstancedNode loaded = (InstancedNode) BinaryExporter.saveAndLoad(assetManager, instancedNode);
+
+        // Verify the control exists after deserialization
+        Assert.assertNotNull("Loaded InstancedNode should not be null", loaded);
+        Assert.assertEquals("InstancedNode should have 1 control after deserialization", 
+                            1, loaded.getNumControls());
+        
+        // Verify the control is the right type
+        Assert.assertNotNull("Control should not be null", loaded.getControl(0));
+    }
+}