Premium Analytics: port Stats Search Terms widget

[dognose24]

Why

Port the Jetpack Stats Search Terms module into Premium Analytics as a standalone widget (`jpa/search-terms`), closing WOOA7S-1496.

The data layer (`useStatsSearchTerms`, `sanitizeStatsSearchTermsResponse`, fixtures, tests) was already complete on trunk. This PR adds only the widget UI layer.

What

• `widgets/search-terms/` — new widget folder following the standard contract:
  • `widget.json` / `widget.ts` — static + live metadata, `jpa/search-terms` name, `search` icon
  • `render.tsx` — `WidgetRoot` + `LeaderboardChart` with `itemLabel` wrapper (mirrors top-platforms pattern for correct bar height), three states (loading / error / empty)
  • `use-search-term-views.ts` — maps `StatsSearchTermsItem[]` → `SearchTermView[]`
  • `style.module.css` — WPDS tokens, container queries
  • `stories/search-terms-widget.stories.tsx` — Default, WithComparison, WidgetDashboardWithWidget
• `src/dashboard-layout.php` — adds `jpa/search-terms` to the default layout at 1×2, order 2

Notes

Search terms data requires organic search traffic from indexed sites. On sites with no search traffic for the selected period, the widget correctly shows an empty state. Selecting a longer date range (e.g. last year) will surface terms if the site has historical search data.

Test plan

• Build: `jetpack build packages/premium-analytics`
• Widget appears in the dashboard widget picker
• With a site that has search terms data: rows render with correct bar proportions
• Empty state shows when no data for the selected period
• Storybook: `Default`, `WithComparison`, `WidgetDashboardWithWidget` stories render

🤖 Generated with Claude Code

[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 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: Please include detailed testing steps, explaining how to test your change, like so:

## Testing instructions:

* Go to '..'
*

---

🔴 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.

If you have questions about anything, reach out in #jetpack-developers for guidance!

---

Premium Analytics plugin:

No scheduled milestone found for this plugin.

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

[jp-launch-control]

Code Coverage Summary

Coverage changed in 1 file.

File	Coverage	Δ%	Δ Uncovered
projects/packages/premium-analytics/src/dashboard-layout.php	0/84 (0.00%)	0.00%	13 💔

Full summary · PHP report

_{Coverage check overridden by Covered by non-unit tests Use to ignore the Code coverage requirement check when E2Es or other non-unit tests cover the code .}