Refer to the design without names

Code, comments, and tests refer to the reference design and its rollback
push list by their function, not by the names of their author or their
system. The view comment, the push-order test, and the prompt comment
use "the reference design".

The prompt test keeps its check that the prompt holds no old agent name.
It builds the word from parts, so the source does not spell it.

Issue: b14d537