Return Exit Code 1 on Failure

Previously, the code returned exit code 0 even when the template
generation failed. Now, if an error occurs, the program will return
exit code 1.

main.go

@@ -53,7 +53,9 @@ func main() {
 	cmd.Flags().StringVar(&args.OutputMode, "output-mode", "single", "Output mode to generate a single file or one file per group ('group' or 'single')")
 	cmd.Flags().IntVar(&args.MaxDepth, "max-depth", 10, "Maximum recursion level for type discovery")
 
-	cmd.Execute()
+	if err := cmd.Execute(); err != nil {
+		os.Exit(1)
+	}
 }
 
 func doRun(_ *cobra.Command, _ []string) error {