How can I edit the subref part specification?

In my MWE below, I apply leandriis’s excellent recipe for creating subschemes using the chemmacros, cleveref, and subcaption packages.

In my scheme captions, I would like to refer to the subschemes using the subref command. How can I make the parts be referred to as (a) and (b), as when I refer to subfigures using subref?

documentclass[oneside,11pt]{book}

usepackage[semibold,tt=false]{libertine}
usepackage{libertinust1math}
usepackage[font={sf,small},labelsep=quad,labelfont=sc]{caption}
usepackage[subrefformat=parens]{subcaption}
usepackage[
  expansion = false ,
  tracking = smallcaps ,
  letterspace = 40 ,
]{microtype}
usepackage{booktabs}
usepackage{acro}
acsetup{
  barriers/use, barriers/reset,
  use-id-as-short,
}
usepackage{chemformula}
setchemformula{charge-hshift=.5pt}
usepackage{chemmacros}
usechemmodule{scheme}

usepackage{graphicx}
usepackage[titles]{tocloft}
setlength{cftfignumwidth}{2.9em}
setlength{cfttabnumwidth}{2.9em}

AtEndPreamble{DeclareCaptionSubType*{scheme}counterwithin{scheme}{chapter}renewcommandthesubscheme{theschemealph{subscheme}}}

usepackage{xpatch}
makeatletter
xapptocmd{@chapter}{addtocontents{los}{protectaddvspace{10p@}}}{}{}
makeatother

usepackage[capitalize]{cleveref}
crefformat{subscheme}{schemename~#2#1#3}

begin{document}

tableofcontents

addcontentsline{toc}{chapter}{listfigurename}
listoffigures

addcontentsline{toc}{chapter}{listschemename}
listofschemes

chapter{First chapter}

% Example subfigure
begin{figure}[!h]
  centering
  begin{subfigure}{0.03textwidth}
    includegraphics[width=textwidth]{example-image-a}%
    phantomsubcaptionlabel{fig:myfigure:a}
  end{subfigure}%
  begin{subfigure}{0.03textwidth}
    includegraphics[width=textwidth]{example-image-b}%
    phantomsubcaptionlabel{fig:myfigure:b}
  end{subfigure}%
  caption{Caption of second figure.
  Part subref{fig:myfigure:a} and part subref{fig:myfigure:b}.}label{fig:myfigure}
end{figure}

% Example subscheme
begin{scheme}[!h]
  centering
  begin{subscheme}{0.03textwidth}
    includegraphics[width=textwidth]{example-image-a}%
    phantomsubcaptionlabel{sch:myscheme:a}
  end{subscheme}%
  begin{subscheme}{0.03textwidth}
    includegraphics[width=textwidth]{example-image-b}%
    phantomsubcaptionlabel{sch:myscheme:b}
  end{subscheme}%
  caption{Caption of third scheme.
  Part subref{sch:myscheme:a} and part subref{sch:myscheme:b}.}label{sch:myscheme}
end{scheme}

Refer to cref{fig:myfigure}, cref{fig:myfigure:a}, and cref{fig:myfigure:b}.
Finally refer to cref{sch:myscheme}, cref{sch:myscheme:a}, and cref{sch:myscheme:b}.

end{document}