`t19` and threat-related numbering are made permanent by current tooling

Originally posted by @TallTed and @msporny in https://github.com/w3c/vc-render-method/pull/65#discussion_r3836547631

[@TallTed] This kind of target href forces the t19 and threat-related numbering to be permanent. I would advise rather that this target (and all the neighbor fragment identifiers) drop the x00 from the fragment ID, and use only the name to form the fragment. This will mean renumbering can happen as often as might be needed or wanted, and the links (like this one) will be unbroken.

[@msporny] I agree, this is a problem, but it is a problem in the current tooling. I'm also arguing for that in the respec-threats extension. I cannot fix that problem now, however, there is much more that needs to change/be updated for that change to go into place.

Issue created for tracking purposes. Hoping we'll get to it in the relatively near future.

Start with the linked discussion in pull request 65 and the respec-threats extension, focusing on how target hrefs and neighboring fragment identifiers are generated. Determine the tooling changes needed so renumbering does not break links; done means threat-related anchors can be renumbered without making their identifiers permanent.