fix: uv cache dir

[dan-fernandes]

UV is currently caching directly into the scratch root, rather than it its own directory.

This puts a subdir .uv-cache inside of the scratch root.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 94.99%. Comparing base (ae766ca) to head (d488b4e).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1336   +/-   ##
=======================================
  Coverage   94.99%   94.99%           
=======================================
  Files          42       42           
  Lines        2755     2755           
=======================================
  Hits         2617     2617           
  Misses        138      138           

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[dan-fernandes]

My original "fix" put the contents of the uv-cache at the root of the scratch directory. The new fix makes a new subdirectory, .uv-cache inside the scratch directory.