Fix DataCloneError by excluding non-serializable cache from state

Excluded blendedImageCache and blendedImageDirty properties from layer serialization in CanvasState.ts to prevent DataCloneError when saving state. This ensures that only serializable data is sent to Web Workers, while runtime caches are regenerated as needed. Blend area performance optimization remains functional without serialization issues.

js/CanvasState.js

@@ -286,6 +286,9 @@ If you see dark images or masks in the output, make sure node_id is set to ${cor
         const preparedLayers = await Promise.all(this.canvas.layers.map(async (layer, index) => {
             const newLayer = { ...layer, imageId: layer.imageId || '' };
             delete newLayer.image;
+            // Remove cache properties that cannot be serialized for the worker
+            delete newLayer.blendedImageCache;
+            delete newLayer.blendedImageDirty;
             if (layer.image instanceof HTMLImageElement) {
                 if (layer.imageId) {
                     newLayer.imageId = layer.imageId;