fix: correct Dropdown keyboard typing detection logic

[naaa760]

Closes #20842

Changelog

Changed

• Fixed keyboard typing detection logic in Dropdown component

Testing / Reviewing

1. Test arrow key navigation doesn't trigger typing mode
2. Verify Space/Enter open dropdown correctly
3. Test typing letters enters typing mode with proper timer reset

PR Checklist

• Reviewed every line of the diff
• Addressed any impact on accessibility (a11y)

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 92.58%. Comparing base (b486103) to head (a31e736).

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #20860      +/-   ##
==========================================
- Coverage   92.62%   92.58%   -0.04%     
==========================================
  Files         515      515              
  Lines       38222    38224       +2     
  Branches     5861     5802      -59     
==========================================
- Hits        35403    35391      -12     
- Misses       2669     2684      +15     
+ Partials      150      149       -1     

Flag	Coverage Δ
main-packages	85.57% <100.00%> (-0.04%)	⬇️
web-components	96.87% <ø> (ø)

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