fix: CIワークフローのコード生成コマンドを修正

- build_runnerの実行コマンドをdartからflutterに変更し、正しい環境でのコード生成を実施

Author: LibraryLibrarian

.github/workflows/ci.yaml

@@ -68,7 +68,26 @@ jobs:
       - name: Codegen verify (only latest)
         if: matrix.flutter == '3.32.x'
         run: |
-          dart run build_runner build -d --build-filter="lib/**"
+          set -e
+          # Locate frontend_server snapshot across engine layouts
+          SNAP=""
+          for C in \
+            "$FLUTTER_ROOT/bin/cache/artifacts/engine/linux-x64/frontend_server.dart.snapshot" \
+            "$FLUTTER_ROOT/bin/cache/artifacts/engine/common/frontend_server.dart.snapshot"; do
+            if [ -f "$C" ]; then SNAP="$C"; break; fi
+          done
+          if [ -z "$SNAP" ]; then
+            SNAP=$(find "$FLUTTER_ROOT/bin/cache/artifacts/engine" -name frontend_server.dart.snapshot | head -n1 || true)
+          fi
+          if [ -z "$SNAP" ] || [ ! -f "$SNAP" ]; then
+            echo 'frontend_server snapshot not found'
+            ls -R "$FLUTTER_ROOT/bin/cache/artifacts/engine" || true
+            exit 1
+          fi
+          export FLUTTER_FRONTEND_SERVER_SNAPSHOT="$SNAP"
+          echo "Using frontend_server: $FLUTTER_FRONTEND_SERVER_SNAPSHOT"
+          flutter pub get
+          flutter pub run build_runner build -d --build-filter="lib/**"
           git diff --exit-code || (echo 'Codegen produced changes. Please commit generated files.' && exit 1)
 
   example-android: