refactor(output): share the JSON, created-resource and batch tails

Mutations end with a.jsonResult or a.created instead of hand-rolled
--json branches, the two identical jsonResult/writeMutationJSON helpers
become one, and writeBatchJSON checks --json itself so batch commands
share one tail.

Signed-off-by: bircni <bircni@icloud.com>

internal/app/repository_migrate.go

@@ -143,10 +143,7 @@ $ tea repo migrate https://github.com/acme/tool --service github --issues --pull
 				detail = " (pull mirror)"
 			}
 			a.done(cmd, "Imported %s into %s%s", opts.CloneURL, item.FullName, detail)
-			if a.options.json != "" {
-				return a.writeJSON(cmd, item)
-			}
-			return a.printURL(cmd, item.URL)
+			return a.created(cmd, item, item.URL)
 		},
 	}
 	flags := command.Flags()