- Add test for xargs without _max_length parameter (lazy evaluation)
- Add test for xargs with explicit _max_length parameter
- Both tests use subprocess approach to verify actual xargs execution
- Tests verify fix works at runtime, not just import time
- Add subprocess-based test to expose import-time os.sysconf bug
- Test runs in fresh subprocess to avoid conftest.py import issues
- Test fails with current buggy implementation, will pass after fix