Release v0.2.2 — MkDocs documentation infrastructure

[NanoBiostructuresRG]

Summary

Documentation infrastructure — no changes to source code, public API, or test suite.

Changes

• MkDocs + Material theme + mkdocstrings setup
• docs/index.md — home page
• docs/api.md — auto-generated API reference from NumPy docstrings
• docs/changelog.md — changelog page via snippets
• mkdocs.yml — configuration with Material theme and mkdocstrings plugin
• .github/workflows/docs.yml — auto-deploy to GitHub Pages on push to main
• API.md removed — replaced by auto-generated docs
• Documentation URL added to pyproject.toml

Checklist

• 146 tests passing locally
• CI green on Python 3.11 and 3.12
• GitHub Pages source set to GitHub Actions