src: include filesystem root in package search

[Archkon]

Move the root termination check after processing the current directory so node --run can find package.json and node_modules/.bin at the filesystem root.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 90.29%. Comparing base (a4aa3c0) to head (9f54a09).

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #64909      +/-   ##
==========================================
+ Coverage   90.28%   90.29%   +0.01%     
==========================================
  Files         760      760              
  Lines      247061   247063       +2     
  Branches    46592    46585       -7     
==========================================
+ Hits       223058   223088      +30     
+ Misses      15491    15448      -43     
- Partials     8512     8527      +15     

Files with missing lines	Coverage Δ
src/node_task_runner.cc	88.88% <100.00%> (-0.44%)	⬇️

... and 33 files with indirect coverage changes

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