A pre-processor fable

[Rob Beezer]

Anthropic released a "Fable 5" model yesterday, this is the safer version of the
much-discussed Mythos model (no bio, no cybersecurity).

You won't be surprised that I tried it immediately. Just asked it to "analyze"
the assembly (pre-processor) stylesheet, which always gives me heartburn. I
provided very little guidance. Did not seem to think much about the code
comments, so I guess I need to ask for another pass, since I know they could use
some work.

* Found several apparent bugs.

* Of 15 passes, one was folded into another, and two are related to features
that a project may not have, so those passes are now conditional.

* The reduction in passes saves a few percent on run time. Nothing anybody
will notice, but we do not have much run-time left to chip away at, so every bit
is a win.

Rob

https://github.com/PreTeXtBook/pretext/pull/2909

https://github.com/PreTeXtBook/pretext/pull/2910