fix: update focus-visible box-shadow to use CSS variable

[Th3S4mur41]

closes #1278

This pull request makes a minor update to the focus styling in the media-text-display component, allowing the box shadow to be customized via a CSS variable.

• Accessibility and customization:
  • src/js/media-text-display.ts: Updated the :host(:focus-visible) selector to use the --media-focus-box-shadow CSS variable, enabling easier customization of the focus box shadow.

---

Note

Low Risk
A small, CSS-only change limited to focus-visible styling; functional behavior is unchanged aside from allowing theming overrides.

Overview
Updates media-text-display focus styling so :host(:focus-visible) uses a configurable CSS custom property (--media-focus-box-shadow) with the previous inset shadow as the fallback.

^{Written by Cursor Bugbot for commit 5c97f11. This will update automatically on new commits. Configure here.}

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 73.58%. Comparing base (3ea80df) to head (5c97f11).
⚠️ Report is 295 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1279      +/-   ##
==========================================
- Coverage   78.55%   73.58%   -4.97%     
==========================================
  Files          59       56       -3     
  Lines       11080    13873    +2793     
  Branches        0      783     +783     
==========================================
+ Hits         8704    10209    +1505     
- Misses       2376     3631    +1255     
- Partials        0       33      +33     

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