feat(yoast): use shared primary category utility from newspack-plugin

[rbcorrales]

All Submissions:

• Have you followed the Newspack Contributing guideline?
• Does your code follow the WordPress' coding standards and VIP Go coding standards?
• Have you checked to ensure there aren't other open Pull Requests for the same update/change?

Changes proposed in this Pull Request:

Replaces inline Yoast WPSEO_Primary_Term logic in the classic theme with the shared Newspack\Primary_Category utility from newspack-plugin (see Automattic/newspack-plugin#4563).

Changes:

• newspack_categories() in template-tags.php now calls the shared utility with a class_exists guard, falling back to all categories when the plugin is not active
• Body class logic in template-functions.php uses the shared utility for the primary-cat-* class
• Removed the post_primary_category Customizer toggle (the setting now lives in Newspack > Settings > Advanced Settings)

The plugin handles backwards compatibility: sites that had the old Customizer toggle disabled will remain disabled until an admin explicitly changes it via the new settings UI, at which point the legacy theme mod is cleaned up.

Depends on Automattic/newspack-plugin#4563.

Closes NPPD-1346.

How to test the changes in this Pull Request:

1. Activate the classic Newspack theme with Yoast SEO and newspack-plugin (with PR #4563) active.
2. Create a post with multiple categories, set one as primary via Yoast.
3. View the post. Only the primary category should display.
4. Go to Newspack > Settings > Advanced Settings. Toggle off. View the post. All categories should display.
5. Deactivate newspack-plugin entirely. View the post. All categories should display (graceful fallback).
6. Verify the Customizer no longer shows the "Use Yoast's primary category functionality" checkbox.

Other information:

• Have you added an explanation of what your changes do and why you'd like us to include them?
• Have you written new tests for your changes, as applicable?
• Have you successfully ran tests with your changes locally?

[Copilot]

Pull request overview

This PR updates the classic Newspack theme’s Yoast primary category handling to use the shared Newspack\Primary_Category utility provided by newspack-plugin, and removes the now-relocated Customizer toggle.

Changes:

• Updated newspack_categories() to use Newspack\Primary_Category::get() when available, falling back to the standard category list otherwise.
• Updated newspack_body_classes() to add the primary-cat-* class using the shared utility when available.
• Removed the legacy post_primary_category Customizer setting/control.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
newspack-theme/inc/template-tags.php	Uses Newspack\Primary_Category when available; otherwise falls back to get_the_category_list().
newspack-theme/inc/template-functions.php	Computes primary-cat-* body class via the shared utility when available.
newspack-theme/inc/customizer.php	Removes the old Customizer toggle for Yoast primary category behavior.

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[laurelfulford]

Looks good! That Customizer panel is getting empty!

[github-actions]

Hey @rbcorrales, good job getting this PR merged! 🎉

Now, the needs-changelog label has been added to it.

Please check if this PR needs to be included in the "Upcoming Changes" and "Release Notes" doc. If it doesn't, simply remove the label.

If it does, please add an entry to our shared document, with screenshots and testing instructions if applicable, then remove the label.

Thank you! ❤️

[github-actions]

🎉 This PR is included in version 2.21.0-alpha.1 🎉

The release is available on GitHub release

Your semantic-release bot 📦🚀

[github-actions]

🎉 This PR is included in version 2.21.0 🎉

The release is available on GitHub release

Your semantic-release bot 📦🚀