Add C++ API documentation

[awvwgk]

• add GitHub Actions workflow for deploying pages
• add setup for sphinx + breath to format Doxygen generated documentation
• add pages for molecule, basis set, grid, runtime environment, load balancer, xc integrator and macros
• update header files with doxygen-style comments to display documentation

Deployed at https://awvwgk.github.io/GauXC/api/cxx/

Examples:

[Copilot]

Pull request overview

This PR adds comprehensive C++ API documentation using Doxygen and Sphinx/Breathe. It introduces a GitHub Actions workflow to build and deploy documentation to GitHub Pages, sets up the Sphinx documentation infrastructure, and enhances header files with detailed Doxygen-style comments.

Changes:

• Added GitHub Actions workflow for automated documentation deployment to GitHub Pages
• Set up Sphinx + Breathe toolchain with Doxygen configuration for generating C++ API documentation
• Enhanced header files with comprehensive Doxygen comments for public APIs including XCIntegrator, RuntimeEnvironment, MolGrid, Molecule, Shell, and related classes

Reviewed changes

Copilot reviewed 24 out of 24 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
.github/workflows/docs.yml	GitHub Actions workflow for building Doxygen/Sphinx docs and deploying to Pages
docs/Doxyfile	Doxygen configuration for extracting C++ API documentation
docs/conf.py	Sphinx configuration with Breathe integration and ReadTheDocs support
docs/index.rst	Main documentation landing page
docs/requirements.txt	Python dependencies for Sphinx build (breathe, sphinx, sphinx-book-theme, sphinxcontrib-bibtex)
docs/api/cxx/*.rst	ReStructuredText pages for molecule, basis set, grid, runtime, load balancer, XC integrator, and macros
docs/_static/bib/references.bib	BibTeX references for DFT quadrature schemes
docs/.gitignore	Ignores generated Doxygen output directory
include/gauxc/xc_integrator.hpp	Added comprehensive documentation for XCIntegrator class and all public methods
include/gauxc/xc_integrator_settings.hpp	Documented XC and EXX integrator settings structures
include/gauxc/shell.hpp	Documented Shell class with detailed member and method descriptions
include/gauxc/runtime_environment/decl.hpp	Documented RuntimeEnvironment and DeviceRuntimeEnvironment classes
include/gauxc/molgrid.hpp	Documented MolGrid container class
include/gauxc/molgrid/defaults.hpp	Documented default grid factory and radius/scaling functions
include/gauxc/molecule.hpp	Documented Molecule class representing atom collections
include/gauxc/molecular_weights.hpp	Documented molecular weight partitioning classes
include/gauxc/grid_factory.hpp	Updated enum documentation style for consistency

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.