fix(modal-checkout): retrieve order from query vars in thankyou template

[adekbadek]

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:

When the modal checkout thankyou.php template is used as a replacement for global/form-login.php, WooCommerce does not provide the $order variable. This causes the thank-you page to fail because subsequent code depends on $order being set.

This fix retrieves the order from the URL query vars (order-received) when $order is not available, using the same approach WooCommerce uses in its order-received endpoint.

How to test the changes in this Pull Request:

1. On trunk,
2. Set up a Newspack site with WooCommerce and the modal checkout enabled (donations or memberships).
3. Open the modal checkout
4. Observe the logged warning:

5. Switch to this branch, observe the warning gone

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 fixes a modal-checkout thank-you template edge case where WooCommerce doesn’t provide an $order object (notably when the template is used as a replacement for global/form-login.php), by reconstructing the order from the request so the thank-you UI can render reliably.

Changes:

• Adds a fallback to load the WooCommerce order from the order-received query var when $order is not already set.
• Keeps the existing order-key validation guard (key + hash_equals) to prevent displaying order details for invalid URLs.

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[github-actions]

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

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[github-actions]

🎉 This PR is included in version 4.26.2-alpha.1 🎉

The release is available on:

• npm package (@alpha dist-tag)
• GitHub release

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