fix(toolkit-lib): "refactor" never releases reader lock or cleans up temp dir

[rix0rrr]

The refactor operation was not using await using on the assembly that it got from assemblyFromSource, causing it to never be cleaned up.

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[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 79.41%. Comparing base (90579c3) to head (6e5c6ae).

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #700   +/-   ##
=======================================
  Coverage   79.41%   79.41%           
=======================================
  Files          49       49           
  Lines        7358     7358           
  Branches      817      818    +1     
=======================================
  Hits         5843     5843           
  Misses       1496     1496           
  Partials       19       19           

Flag	Coverage Δ
suite.unit	79.41% <ø> (ø)

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