chore: Fix border radius bug on segmented-control

[at-susie]

Description

Fixes a bug in the segmented control’s border-radius styling. Previously, each segment used the same radius as borderRadiusButton. Because the inner segments are shorter than the button height, customizing borderRadiusButton could result in visibly misaligned corner radii compared to the outer border (see attached image).

This change does not affect the default styling, but improves visual consistency when borderRadiusButton is customized.

Related links, issue #, if available: n/a

How has this been tested?

Review checklist

The following items are to be evaluated by the author(s) and the reviewer(s).

Correctness

• Changes include appropriate documentation updates.
• Changes are backward-compatible if not indicated, see CONTRIBUTING.md.
• Changes do not include unsupported browser features, see CONTRIBUTING.md.
• Changes were manually tested for accessibility, see accessibility guidelines.

Security

• If the code handles URLs: all URLs are validated through the checkSafeUrl function.

Testing

• Changes are covered with new/existing unit tests?
• Changes are covered with new/existing integration tests?

---

By submitting this pull request, I confirm that you can use, modify, copy, and redistribute this contribution, under the terms of your choice.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 97.45%. Comparing base (a6cdcd0) to head (ce85ad6).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #4398   +/-   ##
=======================================
  Coverage   97.45%   97.45%           
=======================================
  Files         909      909           
  Lines       26637    26637           
  Branches     9614     9615    +1     
=======================================
  Hits        25958    25958           
+ Misses        673      636   -37     
- Partials        6       43   +37     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.