style(core): apply clang-format to source files

[LessUp]

Summary

• run clang-format across src/include/tests to match CI expectations
• keep the previous repository simplification and CUDA preset changes untouched

Validation

• find src include tests -type f ( -name ".cpp" -o -name ".h" -o -name "*.cu" ) | xargs clang-format-19 --dry-run --Werror
• cmake --build --preset cuda-linux && ctest --preset cuda-linux
• cmake --build build-no-cuda && ctest --test-dir build-no-cuda --output-on-failure