test(cli): clean up multi-output test files in afterAll

[knoan]

Summary

• Add afterAll hook to clean up multi1.peggy, multi2.peggy, and the multi-out directory after the --multi-output test suite completes

Fixes #652

Test plan

• Tests pass with npm test -- -t "multi-output"
• Verified no leftover files remain after test execution

🤖 Generated with Claude Code

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 99.48%. Comparing base (ddcb829) to head (849bcc4).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #653   +/-   ##
=======================================
  Coverage   99.48%   99.48%           
=======================================
  Files          34       34           
  Lines        4313     4313           
=======================================
  Hits         4291     4291           
  Misses         22       22           

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[hildjj]

Thanks!