Fix listener array copy in emit

[Constantiner]

Summary

• ensure emit iterates over a snapshot of listeners
• test unsubscribing during emit does not skip callbacks

Testing

• npm test

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https://chatgpt.com/codex/tasks/task_e_683f48053af08327bb6e0a762a3d72d9

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 100.00%. Comparing base (5efd1d4) to head (5574a9e).

Additional details and impacted files

@@            Coverage Diff            @@
##              main        #5   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files            1         1           
  Lines           95        96    +1     
  Branches        15        15           
=========================================
+ Hits            95        96    +1     

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