[dependabot]

• Closes https://github.com/ComPWA/.github-private/issues/23
• Closes https://github.com/ComPWA/.github-private/issues/28
• Closes https://github.com/ComPWA/.github-private/issues/35

🖱️ Developer experience

• Pull requests now request a review from @ComPWA/maintainers automatically through a new CODEOWNERS file.
• Documentation can use GitHub-style alerts such as > [!TIP], which also render on GitHub, through the MyST alert extension (myst-parser>=5.1); existing admonitions use this syntax now.

🔨 Maintenance

• Read the Docs installs the doc dependency group with its native uv support instead of a custom Pixi install script, and fails the build on Sphinx warnings.
• Optional attrs converters keep their input and output types, so the upgraded ty accepts the particle and edge definitions.
• test_solving.py expects the two additional solutions that the upgraded dependencies produce.

Squash commit messages

* DX: use GitHub-style alerts in the documentation
* MAINT: build Read the Docs with its native uv support
* MAINT: type optional attrs converters