Use C++20 standard for clang-tidy to avoid C++23 module issues

Co-authored-by: jwinarske <12262875+jwinarske@users.noreply.github.com>

Author: Copilot

.github/workflows/ci.yml

@@ -124,7 +124,7 @@ jobs:
           cmake .. -GNinja \
             -DCMAKE_BUILD_TYPE=Release \
             -DCMAKE_EXPORT_COMPILE_COMMANDS=ON \
-            -DCMAKE_CXX_FLAGS="-fno-modules"
+            -DCMAKE_CXX_STANDARD=20
         env:
           CC: clang
           CXX: clang++