fix(HeaderPanel): replace hardcoded prefix in CSS selector

[emyarod]

Closes #16908

replaces hardcoded CSS prefix

Changelog

• CSS prefix in blur listener

Testing / Reviewing

confirm that the component behavior on blur remains unchanged

[netlify]

✅ Deploy Preview for carbon-elements ready!

Name	Link
🔨 Latest commit	d2ee9dc
🔍 Latest deploy log	https://app.netlify.com/sites/carbon-elements/deploys/66e33b7581ea6d0008008967
😎 Deploy Preview	https://deploy-preview-17422--carbon-elements.netlify.app
📱 Preview on mobile	Toggle QR Code... Use your smartphone camera to open QR code link.

---

To edit notification comments on pull requests, go to your Netlify site configuration.

[netlify]

✅ Deploy Preview for v11-carbon-react ready!

Name	Link
🔨 Latest commit	d2ee9dc
🔍 Latest deploy log	https://app.netlify.com/sites/v11-carbon-react/deploys/66e33b7561cb20000895d3e1
😎 Deploy Preview	https://deploy-preview-17422--v11-carbon-react.netlify.app
📱 Preview on mobile	Toggle QR Code... Use your smartphone camera to open QR code link.

---

To edit notification comments on pull requests, go to your Netlify site configuration.

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 1 line in your changes missing coverage. Please review.

Project coverage is 76.82%. Comparing base (fdb31d9) to head (d2ee9dc).
Report is 4 commits behind head on main.

Files with missing lines	Patch %	Lines
...kages/react/src/components/UIShell/HeaderPanel.tsx	0.00%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main   #17422   +/-   ##
=======================================
  Coverage   76.82%   76.82%           
=======================================
  Files         408      408           
  Lines       13973    13973           
  Branches     4341     4341           
=======================================
  Hits        10735    10735           
  Misses       3064     3064           
  Partials      174      174           

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