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/branches.go

@@ -196,7 +196,7 @@ $ tea branch create bisect --source 3f2a9c1`,
 			} else {
 				a.done(cmd, "Created branch %s from %s in %s at %s", item.Name, source, target.Repo, shortSHA(item.SHA))
 			}
-			return a.writeMutationJSON(cmd, item)
+			return a.jsonResult(cmd, item)
 		},
 	}
 	command.Flags().StringVarP(&source, "source", "s", "", "Branch, tag or commit to start from (default: the default branch)")