feat(canvas): add helpers to detect transparent clipboard nodes

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

frontend/src/ui/pages/CanvasWorkspace/index.tsx

@@ -5024,6 +5024,21 @@ function canvasBackgroundStorageKey(projectId: string) {
   return `fluxo:canvas-background:${projectId}`;
 }
 
+function isTransparentClipboardNode(node: CanvasNode) {
+  return node.type === "image" && (node.layerRole === "background-removed" || node.tone === "transparent-image");
+}
+
+async function shouldUseInternalClipboardNode(node: CanvasNode, imageFiles: File[]) {
+  const imageFile = imageFiles[0];
+  if (!imageFile) return false;
+  try {
+    const dimensions = await readImageDimensions(imageFile);
+    return dimensions.width === Math.max(1, Math.round(node.width)) && dimensions.height === Math.max(1, Math.round(node.height));
+  } catch {
+    return false;
+  }
+}
+
 async function writeCanvasNodeToSystemClipboard(node: CanvasNode) {
   if (node.type === "text") {
     await writeClipboardText(node.content || node.title);