System queries with Lua: l3sys-query [.tex]

[Karl Berry]

    /usr/local/texlive/2024/texmf-dist/tex/latex/tools/.tex

.tex is special-cased in the kpse code precisely because LaTeX
provides/requires it.
.. (line 1280 of kpathsea/tex-file.c)
          && !STREQ (q, ".tex")                 /* specially allow .tex     */

So it's necessary to do any (TeX) testing with a different .filename. -k