Suppress page number on standout slides

The black page number is illegible against the dark standout background.
Defines a custom frame numbering template that outputs nothing on standout
frames and the normal fraction on all others.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

slides_template/example.tex

@@ -169,6 +169,14 @@ BoldItalicFont  =   *-BoldItalic
 % remove the nagivation symbols
 \setbeamertemplate{navigation symbols}{}
 
+% suppress page number on standout slides
+\defbeamertemplate{frame numbering}{fraction-no-standout}{%
+  \ifthenelse{\boolean{metropolis@standout}}%
+    {}%
+    {\insertframenumber/\inserttotalframenumber}%
+}
+\setbeamertemplate{frame numbering}[fraction-no-standout]
+
 \newcommand{\credit}[1]{%
   \tikz[overlay]{\node at (current page.south west)
     [anchor=south west, yshift=3pt, xshift=2pt]