When reading the docs generated by JOBNAME/pipeline-syntax/globals#manager, it's awfully unclear that "manager" is part of the postbuild plugin.

It'd be good to mention in the description that it's from the postbuild plugin, and the validity rules around when you can use it.

I got quite lost for some time trying to figure out why `manager.listener.logger.println` in one of my global library `vars/` methods wasn't seeming to do anything at all.

(JENKINS-54442 relates to the broder issue)