build(space): install fonts-raleway and fonts-lato in postBuild to satisfy fontspec without modifying template

postBuild

@@ -1,6 +1,14 @@
 #!/usr/bin/env bash
 set -euo pipefail
 
+echo "[postBuild] Installing system fonts (Raleway, Lato) for fontspec"
+if command -v apt-get >/dev/null 2>&1; then
+  apt-get update && apt-get install -y fonts-raleway fonts-lato fonts-dejavu-core fonts-dejavu-extra || true
+  fc-cache -f -v || true
+else
+  echo "[postBuild] apt-get not available; skipping font install"
+fi
+
 echo "[postBuild] Installing Tectonic"
 bash install_tectonic.sh || echo "[postBuild] Tectonic install script returned non-zero; continuing."
 

template/beamerthemegemini.sty

@@ -15,17 +15,39 @@
 % Fonts
 % ====================
 
-\newfontfamily\Raleway[Ligatures=TeX]{Raleway}
-\newfontfamily\Lato[Ligatures=TeX]{Lato}
-
+% Prefer Raleway/Lato if available; otherwise fall back to DejaVu or Latin Modern Sans
 \usefonttheme{professionalfonts}
 
-\setsansfont{Lato}[
-  UprightFont=*-Light,
-  ItalicFont=*-LightItalic,
-  BoldFont=*-Regular,
-  BoldItalicFont=*-Italic
-]
+\IfFontExistsTF{Raleway}{
+  \newfontfamily\Raleway[Ligatures=TeX]{Raleway}
+}{
+  \newfontfamily\Raleway[Ligatures=TeX]{DejaVu Sans}
+}
+
+\IfFontExistsTF{Lato}{
+  \newfontfamily\Lato[Ligatures=TeX]{Lato}
+}{
+  \newfontfamily\Lato[Ligatures=TeX]{DejaVu Sans}
+}
+
+\IfFontExistsTF{Lato}{
+  \setsansfont{Lato}[
+    UprightFont=*-Light,
+    ItalicFont=*-LightItalic,
+    BoldFont=*-Regular,
+    BoldItalicFont=*-Italic
+  ]
+}{
+  \IfFontExistsTF{DejaVu Sans}{
+    \setsansfont{DejaVu Sans}[
+      BoldFont=*-Bold,
+      ItalicFont=*-Oblique,
+      BoldItalicFont=*-BoldOblique
+    ]
+  }{
+    \setsansfont{Latin Modern Sans}
+  }
+}
 
 \setbeamerfont{headline}{family=\Raleway}
 \setbeamerfont{headline title}{size=\Huge,series=\bfseries}