Restyle the documentation with a VHDL API reference and release docs

[ru551n]

Follow-up to #25, which was merged with its first two commits only. This PR has the rest: the documentation restyled with the Read the Docs theme and a page per topic, a VHDL API reference, and Read the Docs builds of each release.

Documentation

• Theme: sphinx_rtd_theme. The sidebar is grouped into User guide, VHDL API reference, Simulators and About, with previous/next buttons and an "Edit on GitHub" link on every page.
• Landing page: badges (documentation, repository, PyPI, Python versions, license, CI), what the package is, key features linking to their pages, the supported simulators and a quick start.
• User guide: user_guide.rst is split into a page per topic: Requirements, Running Python code (python_setup/python_cleanup, exec, eval, call), Types, Errors and semantics, Sessions, Python files and modules, File paths, How it works, Other simulators. The text is unchanged apart from cross-page references, and every python_bridge:* label still resolves.
• VHDL API reference: a page per package of python_context, generated at build time from the package declarations by docs/vhdl_api.py, so it follows the code, the generated python_pkg.vhd included.
  • Every public declaration is shown with the comment above it, under the sections of the source.
  • A linked list of the names is at the top of each page.
  • p_* names and private sections are left out.
• Release notes: a page generated from release_notes/*.md, newest first. A version newer than pyproject.toml is titled "Unreleased". release in conf.py now comes from pyproject.toml.
• README: the badges of the landing page, and a link to vunit-python-bridge.readthedocs.io.
• docs/requirements.txt also pins sphinx-rtd-theme 3.1.0 and myst-parser 5.1.0.

Release docs

The Read the Docs job of the docs workflow now also handles a release tag vX.Y.Z. It:

1. syncs the versions of the project,
2. waits for the version of the tag,
3. activates it,
4. builds it and stable.

Each release then has docs of its own at /en/vX.Y.Z/. A push to main still builds latest.

Open PRs

#11, #15, #16, #18, #21 and #26 edit docs/user_guide.rst. When rebased, their doc changes move to the matching page. #15 also adds python_object_pkg to PACKAGES in docs/vhdl_api.py.

Tests

• The docs build with -W without warnings locally, also at the restyle commit on its own.
• actionlint passes on the workflow.
• The release path runs for the first time at the next tag.

🤖 Generated with Claude Code