feat: CI-Compiler auf Clang 18 umgestellt (GCC→Clang)

- CI: g++-13 → clang++-18 mit explizitem CMAKE_CXX_COMPILER
- Devbox: gcc@13 → clang@18, CC/CXX auf clang/clang++
- Ziel: gleicher Compiler (Clang) auf macOS und Ubuntu
- CMakeLists.txt Clang-Sektion bereits plattformneutral (AppleClang + LLVM Clang)

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

.github/workflows/ci.yml

@@ -13,7 +13,7 @@ concurrency:
 
 jobs:
   build-and-test:
-    name: "${{ matrix.os }} · C++${{ matrix.cxx_std }}"
+    name: "${{ matrix.os }} · Clang · C++${{ matrix.cxx_std }}"
     runs-on: ${{ matrix.os }}
     strategy:
       fail-fast: false
@@ -28,13 +28,12 @@ jobs:
       - name: Install dependencies (Linux)
         run: |
           sudo apt-get update -qq
-          sudo apt-get install -y -qq ninja-build cmake g++-13
-          sudo update-alternatives --install /usr/bin/gcc gcc /usr/bin/gcc-13 100
-          sudo update-alternatives --install /usr/bin/g++ g++ /usr/bin/g++-13 100
+          sudo apt-get install -y -qq ninja-build cmake clang-18
 
       - name: CMake configure
         run: |
           cmake -B build -G Ninja \
+            -DCMAKE_CXX_COMPILER=clang++-18 \
             -DCMAKE_CXX_STANDARD=${{ matrix.cxx_std }} \
             -DBUILD_TESTS=ON \
             -DCMAKE_BUILD_TYPE=Release \

devbox.json

@@ -3,7 +3,7 @@
   "packages": [
     "cmake@3.28",
     "ninja@1.11",
-    "gcc@13",
+    "clang@18",
     "zlib@1.3",
     "git@2.44",
     "gdb@14",
@@ -17,8 +17,8 @@
     "fd@9.0"
   ],
   "env": {
-    "CC": "gcc",
-    "CXX": "g++",
+    "CC": "clang",
+    "CXX": "clang++",
     "CMAKE_BUILD_PARALLEL_LEVEL": "4",
     "CCACHE_DIR": "$DEVBOX_PROJECT_ROOT/.ccache",
     "CCACHE_MAXSIZE": "2G"
@@ -32,7 +32,7 @@
       "echo '  KVAI Abrechnungspruefmaschine'",
       "echo '═══════════════════════════════════════════'",
       "echo ''",
-      "echo '  Compiler :  g++ (GCC 13)'",
+      "echo '  Compiler :  clang++ (Clang 18)'",
       "echo '  Build    :  cmake + ninja'",
       "echo '  Sourcen  :  $SRC_DIR (CMakeLists.txt in $PROJECT_ROOT)'",
       "echo '  ccache   :  aktiviert (max 2 GB)'",