Keyboard copy event and search bar cancellation

[peterychang]

Why are these changes needed?

Keyboard focus location was being lost after a copy event. Header anchor was also not selectable while hidden

Fixes (2), (4), (11), (35)

Related issue number

#5630

Checks

• I've included any doc changes needed for https://microsoft.github.io/autogen/. See https://github.com/microsoft/autogen/blob/main/CONTRIBUTING.md to build and test documentation locally.
• I've added tests (if relevant) corresponding to the changes introduced in this PR.
• I've made sure all auto checks have passed.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 75.58%. Comparing base (97536af) to head (adaa213).
Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #5820   +/-   ##
=======================================
  Coverage   75.58%   75.58%           
=======================================
  Files         189      189           
  Lines       12669    12669           
=======================================
  Hits         9576     9576           
  Misses       3093     3093           

Flag	Coverage Δ
unittests	75.58% <ø> (ø)

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[rysweet]

is custom.js the best filename here?

[peterychang]

is custom.js the best filename here?

Its the default suggested filename (like custom.css)