Non-musical items should be considered when centering percent repeats
From Peter Häring, https://lists.gnu.org/archive/html/bug-lilypond/2023-05/msg00032.html
\version "2.25.5"
{
\repeat percent 4 a'1
\clef bass
a,1
}
The percent repeat sign should be centered between the bar line on its left and the clef on its right.