Add Sphinx documentation with auto-generated API reference

[Hector Hernandez (hectorhdzg)]

• Add Sphinx setup with sphinx-rtd-theme, autodoc, napoleon, and typehints
• Use sphinx-apidoc to auto-generate API reference RSTs from source tree
• Add docs/conf.py, index.rst, Makefile, and make.bat
• Add 'docs' optional dependency group in pyproject.toml
• Add 'docs' tox environment for local and CI builds
• Add docs build job to PR validation CI workflow
• Update .gitignore to exclude docs/_build/ and docs/api/

[Copilot]

Pull request overview

Adds a Sphinx documentation site to the repo and wires it into local/CI tooling so the API reference can be generated from the src/ tree.

Changes:

• Introduces Sphinx configuration and entry docs (docs/conf.py, docs/index.rst) plus standard Makefile/make.bat.
• Adds a docs optional dependency group and a tox -e docs environment that runs sphinx-apidoc and builds HTML.
• Extends PR validation workflow and .gitignore to support docs builds and generated outputs.

Reviewed changes

Copilot reviewed 7 out of 8 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
tox.ini	Adds docs tox environment to generate API RSTs and build Sphinx HTML.
pyproject.toml	Adds docs optional dependencies for Sphinx + theme/typehints.
docs/conf.py	Sphinx configuration (autodoc/napoleon/typehints/intersphinx/theme).
docs/index.rst	Root toctree pointing to generated API reference.
docs/Makefile	Standard Sphinx make entrypoints for local builds.
docs/make.bat	Windows equivalent for local builds.
.gitignore	Ignores generated docs build output and API RSTs.
.github/workflows/pr-validation.yml	Adds CI job to build docs via tox.

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