bug: os.Setenv instead of t.Setenv in toolkit tests — not parallel-safe

[jonchun]

Summary

TestDeployTools uses os.Setenv with manual cleanup instead of t.Setenv(). This is not safe with t.Parallel() and the manual cleanup incorrectly sets the env var to empty string (instead of unsetting) if it was previously unset.

Location

toolkit/toolkit_test.go:217,220

Suggested Fix

Replace with t.Setenv("SHELLGUARD_TOOLKIT_DIR", cacheDir) which handles cleanup automatically.