Take the slide fonts from TeX Live rather than the tree

Open Sans and Roboto Mono ship in texlive-fonts-extra, which the other
templates already require. LuaLaTeX resolves them by family name through
luaotfload, which indexes the TeX tree, so the vendored copies and their
relative Path= keys are unnecessary.

Same faces, pixel-identical output.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

slides_template/fonts.tex

@@ -1,19 +1,7 @@
-% Font setup shared by the slides and by the notes pages that mknotes
-% typesets, so that the two match. Loaded by example.tex directly and passed
-% to mknotes with --preamble.
-%
-% Requires fontspec, which unicode-math pulls in on the slides side. Paths must
-% stay relative to the document directory: LuaTeX fails to resolve a
-% parent-relative Path= and dies with an unhelpful empty-filename error.
+% Shared by the slides and by the notes pages mknotes typesets, so the two
+% match. Both families come from texlive-fonts-extra.
 
-\setsansfont{OpenSans}[
-  Path = fonts/OpenSans/, Extension = .ttf,
-  UprightFont = *-Regular, BoldFont = *-Bold,
-  ItalicFont = *-Italic, BoldItalicFont = *-BoldItalic]
-
-\setmonofont{RobotoMono}[
-  Path = fonts/RobotoMono/, Extension = .ttf,
-  UprightFont = *-Regular, BoldFont = *-Bold,
-  ItalicFont = *-Italic, BoldItalicFont = *-BoldItalic]
+\setsansfont{Open Sans}
+\setmonofont{Roboto Mono}
 
 \renewcommand{\familydefault}{\sfdefault}

slides_template/mknotes

@@ -210,8 +210,8 @@ def build_notes_pdf(pages, width, height, thumb_w, thumb_h, workdir,
     bandwidth = width - thumb_w
 
     # \input rather than the file's contents, so that anything relative inside
-    # it (font paths, say) resolves against the document directory. LaTeX runs
-    # from there even though its output goes to the working directory.
+    # it resolves against the document directory. LaTeX runs from there even
+    # though its output goes to the working directory.
     extra = r"\input{%s}" % preamble if preamble else ""
 
     body = [NOTES_PREAMBLE % {