test: Add UI tests for Heatmaps IndexError fix (#6438)

[Azaya89]

Closes #6232

This PR adds tests to verify that IndexError is properly suppressed when mouse/tap events occur outside the bounds of categorical axes on plots like HeatMaps, preventing crashes when users hover/click outside the plots or on colorbars or legends.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 89.21%. Comparing base (c717261) to head (d1561e5).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #6708   +/-   ##
=======================================
  Coverage   89.20%   89.21%           
=======================================
  Files         332      332           
  Lines       72010    72027   +17     
=======================================
+ Hits        64240    64259   +19     
+ Misses       7770     7768    -2     

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[hoxbro]

I feel like the tests are too synthetic. Could we instead make a UI test that recreates the problem in #6232

[Azaya89]

I feel like the tests are too synthetic. Could we instead make a UI test that recreates the problem in #6232

Are you suggesting I replace the tests with something like the MRE in #6232 or just add the UI tests to these ones already written?

[hoxbro]

I think we should replace the existing tests with a UI test.

[hoxbro]

We should verify that these tests fails, if we are running without the fix in #6438

[hoxbro]

Thank you for adding testing 👍

[github-actions]

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