Description:
Introduce GitHub Actions CI workflow to automatically build and test the H5CPP compiler across multiple operating systems and compilers. This ensures that the Clang/LLVM tooling integration remains portable and consistent.

Acceptance Criteria:

• Add .github/workflows/ci.yml

• Run on push and pull_request to staging and release branches

• Matrix includes:

  • Ubuntu 22.04 with gcc-13, gcc-14, clang-14, clang-15
  • Ubuntu 24.04 with gcc-14, gcc-15, clang-17
  • macOS 13/14 with system clang (brew-installed LLVM as fallback)

• Install llvm-X-dev, clang-X, libclang-X-dev as dependencies

• Configure build with cmake -DCMAKE_CXX_STANDARD=23

• Verify successful build and linking of the compiler executable

• Generate per-matrix badge artifacts and publish to GitHub Pages (badges / badges-staging)

Notes:

• Unlike IEX2H5, HDF5 libraries are not required here.
• Initial tests can be limited to compilation success; no persistence runtime checks needed in the first pass.