[kattni]

Migrates xbuild's documentation from MkDocs and Material for MkDocs to Zensical 0.1.0, with Zensical-native configuration files.

This depends on beeware/beeware-docs-tools#288, which moves the shared docs build to Zensical. Until that PR is merged, the docs dependency group is temporarily pinned to its branch (kattni/beeware-docs-tools@tooling/zensical-migration). The pin is reverted to beeware/beeware-docs-tools@main once #288 merges.

Changes

• docs/config.yml, docs/mkdocs.en.yml and docs/en/SUMMARY.md are replaced by docs/zensical.toml and docs/zensical.en.toml, generated with the docs-tools converter. The converter checked that the result is equivalent to the configuration Zensical reads from the YAML files. The literate-nav navigation is now the nav setting in docs/zensical.toml.
• The duplicate "Using xbuild" nav entry is removed. It pointed at the How-to guides index page a second time. Material hid it (but gave the How-to page a "Previous" link to itself); Zensical shows it as a second sidebar link.
• tox.ini: removed the MkDocs-only DISABLE_MKDOCS_2_WARNING and NO_MKDOCS_2_WARNING settings, and the --source-code=src argument, which docs-tools no longer uses.
• pyproject.toml: the temporary docs-tools pin, and docs/en/SUMMARY.md removed from the rumdl excludes.
• .gitignore: ignores the docs/_build.*.toml files that builds generate.

Verification

The strict Zensical build passes with no issues. Compared with the MkDocs build of main:

• Both builds have 52 pages.
• Article text is identical on 47 pages. The other 5 differ only in docs-tools' shared contribution content, which now describes nav in zensical.toml instead of SUMMARY.md, and Zensical instead of MkDocs.
• Page titles, sidebar navigation, header tabs, "On this page" lists, images and other files are identical. Neither build has broken internal links. The How-to page's "Previous" link now goes to the Android tutorial instead of itself.
• objects.inv is byte-identical. xbuild has no API reference pages, so mkdocstrings generates no content.
• Pages look the same in light and dark mode, apart from the theme's compact search box.

Notes for reviewers

• Removing the duplicate "Using xbuild" nav entry keeps the sidebar the same as before. If a sidebar entry for that section is wanted, it could point at how-to/index.md#using-xbuild instead.

PR Checklist:

• I will abide by the BeeWare Code of Conduct
• I have read and have followed the CONTRIBUTING.md file
• This PR was generated or assisted using an AI tool

Assisted-by: Claude Code (Claude Opus 5.5)