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 92.37%. Comparing base (a4172c3) to head (2bff6d9).
⚠️ Report is 2 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #20860      +/-   ##
==========================================
- Coverage   92.38%   92.37%   -0.02%     
==========================================
  Files         515      515              
  Lines       37629    37631       +2     
  Branches     5738     5793      +55     
==========================================
- Hits        34765    34763       -2     
- Misses       2715     2718       +3     
- Partials      149      150       +1     

Flag	Coverage Δ
main-packages	85.54% <100.00%> (-0.04%)	⬇️
web-components	96.66% <ø> (+<0.01%)	⬆️

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