Replace literal passwords in two testing-agent code samples with
environment-variable reads — the secure, idiomatic pattern for each
framework rather than a placeholder string:
- testing-api-tester.md: 'secure_password' -> process.env.TEST_USER_PASSWORD
- testing-performance-benchmarker.md: 'password123' -> __ENV.TEST_USER_PASSWORD (k6)
Removes the weak-credential examples flagged in #477 and models good
secrets hygiene for anyone copying these snippets.
Closes#477
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>