feat(auto-complete): expose openMenu and closeMenu

[kelsos]

Summary

• Adds openMenu() and closeMenu() to RuiAutoComplete's defineExpose, so consumers can programmatically toggle the dropdown.
• Removes the need for the synthetic input-event workaround when hide-search-input is active (the native input is display: none, so calling .focus() is a no-op and there is no public way to re-open the menu).
• Adds a unit test covering the new exposed methods.

Closes #517

Test plan

• pnpm run typecheck
• pnpm run test:run --testNamePattern="openMenu and closeMenu"

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 84.88%. Comparing base (3b153a3) to head (607759e).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #521      +/-   ##
==========================================
+ Coverage   84.87%   84.88%   +0.01%     
==========================================
  Files         143      143              
  Lines        5209     5213       +4     
  Branches     1553     1553              
==========================================
+ Hits         4421     4425       +4     
  Misses        788      788              

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