Forms: Responses Inbox header improvement

[lezama]

Proposed changes:

• Modernize Forms responses inbox header with improved tab navigation
• Add compact number formatting for response counts (19.8K instead of 19,800)
• Add gray background badges for tab counts with improved spacing
• Implement animated underline indicator for active tab selection
• Add view configuration button to header actions
• Improve mobile responsive layout with stacked rows and left alignment
• Match header padding with page layout for visual consistency

Before

After

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)?

Testing instructions:

1. Navigate to Jetpack → Forms → Responses in wp-admin
2. Verify the Inbox/Spam/Trash tabs display with:
   • Compact count formatting (e.g., "19.8K" instead of "19,800")
   • Gray rounded badges around the numbers
   • Thin animated underline on the active tab
3. Click between tabs and observe the smooth underline animation
4. Verify search bar, filters button, and settings cog icon appear on the right
5. Test mobile view (resize browser to < 600px width):
   • Tabs should appear on first row
   • Search and filter controls should stack on second row
6. Verify all existing functionality still works (filtering, searching, viewing responses)

[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 or WordPress.com Site Helper), and enable the update/forms-responses-header-modernization branch.
• To test on Simple, run the following command on your sandbox:

bin/jetpack-downloader test jetpack update/forms-responses-header-modernization

bin/jetpack-downloader test jetpack-mu-wpcom-plugin update/forms-responses-header-modernization

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

[github-actions]

Thank you for your PR!

When contributing to Jetpack, we have a few suggestions that can help us test and review your patch:

• ✅ Include a description of your PR changes.
  
• 🔴 Add a "[Status]" label (In Progress, Needs Review, ...).
  
• 🔴 Add a "[Type]" label (Bug, Enhancement, Janitorial, Task).
  
• ✅ Add testing instructions.
  
• 🔴 Specify whether this PR includes any changes to data or privacy.
  
• ✅ Add changelog entries to affected projects
  

This comment will be updated as you work on your PR and make changes. If you think that some of those checks are not needed for your PR, please explain why you think so. Thanks for cooperation 🤖

---

🔴 Action required: We would recommend that you add a section to the PR description to specify whether this PR includes any changes to data or privacy, like so:

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

My PR adds *x* and *y*.

---

Follow this PR Review Process:

1. Ensure all required checks appearing at the bottom of this PR are passing.
2. Make sure to test your changes on all platforms that it applies to. You're responsible for the quality of the code you ship.
3. You can use GitHub's Reviewers functionality to request a review.
4. When it's reviewed and merged, you will be pinged in Slack to deploy the changes to WordPress.com simple once the build is done.

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[jp-launch-control]

Code Coverage Summary

6 files are newly checked for coverage. Only the first 5 are listed here.

File	Coverage
projects/js-packages/components/components/tabs/list.tsx	2/36 (5.56%) 💔
projects/js-packages/components/components/tabs/panel.tsx	1/2 (50.00%) 💚
projects/js-packages/components/components/tabs/root.tsx	1/2 (50.00%) 💚
projects/js-packages/components/components/tabs/tab.tsx	2/4 (50.00%) 💚
projects/js-packages/components/components/tabs/index.ts	0/0 (—%) 🤷

Full summary · PHP report · JS report

_{If appropriate, add one of these labels to override the failing coverage check: Covered by non-unit tests Use to ignore the Code coverage requirement check when E2Es or other non-unit tests cover the code Coverage tests to be added later Use to ignore the Code coverage requirement check when tests will be added in a follow-up PR I don't care about code coverage for this PR Use this label to ignore the check for insufficient code coveage.}