Issue #651 save asset node in TerrainEditorController

[neph1]

Fixes #651

[Copilot]

Pull Request Overview

This PR updates the TerrainEditorController to properly save the terrain asset after changes, modernizes thread enqueuing to use lambdas, and cleans up unused imports.

• Always enqueue currentFileObject.saveAsset() after saving alpha layers.
• Replace anonymous Callable classes with lambda expressions for conciseness.
• Remove unused imports and update copyright year.

Comments suppressed due to low confidence (2)

jme3-terrain-editor/src/com/jme3/gde/terraineditor/TerrainEditorController.java:146

• The original conditional logic around setModified was removed, so this now always toggles the flag—even if it wasn't intended; restore the previous checks to avoid inadvertently clearing or setting the modified state.

currentFileObject.setModified(state);

jme3-terrain-editor/src/com/jme3/gde/terraineditor/TerrainEditorController.java:108

• [nitpick] There are many repeated enqueue calls with similar lambda patterns; consider extracting a helper method (e.g., runOnSceneThread(Runnable)) to reduce duplication and improve readability.

SceneApplication.getApplication().enqueue(() -> { doSaveAlphaImages(); return null; });