📝 Fix documentation build guidance

[burgholzer]

🤖 AI text below 🤖

Description

The development recipe builds the Python package before installing LLVM/MLIR,
and the documentation recipe bypasses the checked nox session. Move the native
prerequisite before the first package build and document the supported docs and
linkcheck commands. Describe Core's native Doxygen HTML while preserving Breathe
guidance for other projects.

Extend the existing render-and-format tests to cover Core as well as a generic
repository. Core #2462 consumes the rendered installation,
contribution, and tooling pages.

Validation: all 13 rendering tests passed; uv run prek run --all-files passed.
No runtime API or dependency changes. Hosted CI and human review are pending.
Codex implemented and validated this change under explicit user authorization.

Checklist

• The pull request only contains commits that are focused and relevant to this change.
• I have added appropriate tests that cover the new/changed functionality.
• I have updated the documentation to reflect these changes.
• I have added entries to the changelog for any noteworthy additions, changes, fixes, or removals.
• I have added migration instructions to the upgrade guide (if needed).
• The changes follow the project's style guidelines and introduce no new warnings.
• The changes are fully tested and pass the CI checks.
• I have reviewed my own code changes.

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[burgholzer]

This looks fine to me 👍🏼