feat: capture save-generation response in 3D executor

Store savedFilename and savedFilePath on node data after auto-save
completes, following the same pattern as generateVideoExecutor.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/store/execution/generate3dExecutor.ts

@@ -132,6 +132,14 @@ export async function executeGenerate3D(
           }),
         })
           .then((res) => res.json())
+          .then((saveResult) => {
+            if (saveResult.success && saveResult.filename) {
+              updateNodeData(node.id, {
+                savedFilename: saveResult.filename,
+                savedFilePath: saveResult.filePath,
+              });
+            }
+          })
           .catch((err) => {
             console.error("Failed to save 3D model:", err);
           });