test: Separate mobile and desktop tests for recent scroll fix

[jkuelz]

Description

For more reliable test coverage, this separates mobile and desktop scroll tests for #2987 fix.

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?

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 96.27%. Comparing base (054f1c9) to head (177f68f).
Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff            @@
##             main    #2992    +/-   ##
========================================
  Coverage   96.27%   96.27%            
========================================
  Files         769      769            
  Lines       21764    21764            
  Branches     7438     7038   -400     
========================================
  Hits        20954    20954            
  Misses        802      802            
  Partials        8        8            

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