fix: ensure all timers are cancelled when after staggered race finishes

[bdraco]

There was a race where a TimerHandle could be left lingering

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 100.00%. Comparing base (99edb20) to head (0fd33a0).
Report is 2 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff            @@
##              main      #136   +/-   ##
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  Coverage   100.00%   100.00%           
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  Files            5         5           
  Lines          231       231           
  Branches        47        47           
=========================================
  Hits           231       231           

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