GitHub Actions: Test on macOS 26

[cclauss]

GitHub Actions: Test on macOS 26

macOS 26 -- macOS Tahoe 9.15

• https://www.apple.com/os/macos
• https://github.com/actions/runner-images/releases

Example

Fixes #[Issue Number]

Description

Briefly describe the changes in this pull request.

• [Summary of major changes]
• [Summary of minor changes]
• [Any other relevant information]

Type of Change

Please delete options that are not relevant.

• Test a pre-release version of macOS
• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

How Has This Been Tested?

Please describe the tests that you ran to verify your changes.
Provide instructions so we can reproduce. Please also list any relevant details for your test configuration.

• GitHub Actions

Checklist

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented on my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have used Conventional Commits for my commit messages
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published in downstream modules

Screenshots

Attach screenshots or screen recordings of the changes, if any.

Additional Context

Add any other context or information about the pull request here.