Fix \py@release in custom maketitle by adding \makeatletter guard

\py@release contains @ which is only a letter inside \makeatletter scope.
Without the guard pdflatex aborts with "Missing number, treated as zero".

https://claude.ai/code/session_014hVQ5UrK1B4N9ar4UfYpm4

Author: claude

doc/conf.py

@@ -217,8 +217,11 @@
         "noteBorderColor={rgb}{0.306,0.498,0.627},"
         "warningBorderColor={rgb}{0.761,0.384,0.039},"
     ),
-    # Custom title page with amber header bar, logo, and accent footer
+    # Custom title page with amber header bar, logo, and accent footer.
+    # \makeatletter/\makeatother are required to access \py@release (@ is a
+    # letter in LaTeX package code but not in regular document mode).
     "maketitle": r"""
+\makeatletter
 \begin{titlepage}
   \noindent{\color{dfprimary}\rule{\linewidth}{6pt}}\par
   \vfill
@@ -236,6 +239,7 @@
   \vfill
   \noindent{\color{dfaccent}\rule{\linewidth}{4pt}}\par
 \end{titlepage}
+\makeatother
 """,
 }