Forms: replace jetpack buttons with core button

[CGastrell]

This is a takeover from #45007

Resolves FORMS-83

Proposed changes:

Following the original PR, this is a simpler approach just using core/button to replace jetpack/button

Other information:

• Have you written new tests for your changes, if applicable?
• Have you checked the E2E test CI results, and verified that your changes do not break them?
• Have you tested your changes on WordPress.com, if applicable (if so, you'll see a generated comment below with a script to run)?

Jetpack product discussion

None

Does this pull request change what data or activity we track or use?

No

Testing instructions:

(verbatim from original PR)

1. Existing post smoke-test

   • Open a post containing a Contact Form created before this patch (uses Jetpack Button).
   • Confirm there are no editor errors; publish / update.
   • View front-end and submit the form – it should behave as it always did.

2. New form

   • Insert a fresh Contact Form block.
   • Verify the submit control is a Core Button in a Core Buttons wrapper.
   • Publish and submit on the front-end – spinner, disable state and success/error handling should work.

3. Variations

   • Insert each Contact-Form variation (RSVP, Registration, Feedback, etc.).
   • Confirm each uses a Core Button and submits correctly.

4. Editor layout

   • Editing experience should respect the different core/block options when saving.

[github-actions]

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Jetpack plugin:

The Jetpack plugin has different release cadences depending on the platform:

• WordPress.com Simple releases happen as soon as you deploy your changes after merging this PR (PCYsg-Jjm-p2).
• WoA releases happen weekly.
• Releases to self-hosted sites happen monthly:
  • Scheduled release: January 6, 2026

If you have any questions about the release process, please ask in the #jetpack-releases channel on Slack.

[github-actions]

Are you an Automattician? Please test your changes on all WordPress.com environments to help mitigate accidental explosions.

• To test on WoA, go to the Plugins menu on a WoA dev site. Click on the "Upload" button and follow the upgrade flow to be able to upload, install, and activate the Jetpack Beta plugin. Once the plugin is active, go to Jetpack > Jetpack Beta, select your plugin (Jetpack), and enable the replace/forms-jetpack-buttons-core branch.
• To test on Simple, run the following command on your sandbox:

bin/jetpack-downloader test jetpack replace/forms-jetpack-buttons-core

Interested in more tips and information?

• In your local development environment, use the jetpack rsync command to sync your changes to a WoA dev blog.
• Read more about our development workflow here: PCYsg-eg0-p2
• Figure out when your changes will be shipped to customers here: PCYsg-eg5-p2

[jp-launch-control]

Code Coverage Summary

Coverage changed in 3 files.

File	Coverage	Δ%	Δ Uncovered
projects/packages/forms/src/contact-form/class-contact-form.php	968/1397 (69.29%)	-1.50%	30 💔
projects/packages/forms/src/blocks/contact-form/edit.tsx	0/276 (0.00%)	0.00%	3 ❤️‍🩹
projects/packages/forms/src/blocks/contact-form/class-contact-form-block.php	507/592 (85.64%)	3.21%	-19 💚

Full summary · PHP report · JS report

_{Coverage check overridden by Coverage tests to be added later Use to ignore the Code coverage requirement check when tests will be added in a follow-up PR .}

[enejb]

This adds a second spinner next to each button.
We should either remove this one or the one that is in the HTML since they there is really no need to have two.

[simison]

Fix in:

• Forms: Fix multi-step form submit button spinner CSS selector #46807