AI prompting tweaks

This is essentially a scaled-back variant of @Vost's !11545 (closed).

It adopts:

1. The text part of the age token changes, which seem to work well.
2. The deweighting of the expression prompts, and a fine-tuned version of the indifferent expression change which serves to avoid a couple of cases that could generate a bad random (usually smiling) expressions for medium-obedience slaves.
3. Several smaller tweaks.

I suspect the facial beauty changes will also be good but I haven't tested them yet. The existing prompts don't make sense and AIAnon hasn't reappeared to explain them.

Muscle prompts do need tweaking but I'm not satisfied with the proposed changes. I might cook up something else for that.

merged

mentioned in commit 67df5d63