Update Sphinx to 8.x

[MaxGhenis]

Summary

Sphinx 8.2.3 is the latest stable version (released March 2025). Our project currently restricts Sphinx to <6.0.0, which is significantly outdated.

Current Version

"sphinx>=5.0.0,<6.0.0"

Proposed Update

Update to "sphinx>=8.0.0,<9.0.0" to use modern Sphinx versions.

Benefits

• Access to 3+ years of improvements since Sphinx 5.x
• Better Python 3.12/3.13 support
• Improved performance and features
• Better theme compatibility
• Enhanced extension ecosystem

Migration Considerations

• Major version jump from 5.x to 8.x may require configuration updates
• Some deprecated features may have been removed
• Extension compatibility should be verified

Tasks

• Update pyproject.toml to allow Sphinx 8.x
• Test documentation build with Sphinx 8.2.3
• Update sphinx configuration if needed
• Verify all sphinx extensions are compatible
• Fix any deprecation warnings