bibtex doesn't handle escapes properly

There are three kinds of mishandled escapes below:

• bibtex escapes:
  • escaping # when it appears in a string \#. The \ gets rendered as a URL escape character, but should have been ignored.
  • escaping capital letters {CPS}. This escapes gets rendered as capital but eats the whitespace following it.
• latex such as {\"u} and {$\Sigma$}.

I suppose handling the latex escapes is non-trivial, but the bibtex escapes should probably be handled properly. Could possibly handle the latex escapes by passing them on as literal, and assuming the backend knows how to handle them.

#lang scribble/base
@(require
  racket/dict
  racket/port
  scriblib/bibtex
  scriblib/autobib
  rackunit)

@(require/expose scriblib/bibtex (generate-bib))

@(define mybibs
  (call-with-input-string
     @string-append|{@Article{bowman2018:cps-sigma,
       author   = {Bowman, William J. and Cong, Youyou and Rioux, Nick and Ahmed, Amal},
       title    = {Type-preserving {CPS} Translation of {$\Sigma$} and {$\Pi$} Types Is Not Not Possible},
       url      = {https://www.williamjbowman.com/papers\#cps-sigma},
       journal  = {Proceedings of the {ACM} on Programming Languages},
       year = 2018,
     }

     @Article{flueckiger2018:jit,
       author    = {Fl{\"u}ckiger, Olivier and Scherer, Gabriel and Yee, Ming-Ho and Goel, Aviral and Ahmed, Amal and Vitek, Jan},
       title     = {Correctness of speculative optimizations with dynamic deoptimization},
       year = 2018,
       journal  = {Proceedings of the {ACM} on Programming Languages},
       }}| bibtex-parse))

@(define-cite a~cite acitet generate-bibliography)

@(define (~cite str)
  (a~cite (generate-bib mybibs str)))

@~cite{bowman2018:cps-sigma}
@~cite{flueckiger2018:jit}

@(generate-bibliography)

Start with the supplied scriblib/bibtex example, especially bibtex-parse and the generate-bib entry point, and reproduce the three escape cases. Done means BibTeX escapes no longer encode the URL hash or consume following whitespace, with the LaTeX escape behavior made explicit for the shown inputs.