- Move imports to module level in all *_core.py test files (16 files)
- Remove try/except/skip patterns from integration tests
- Remove @pytest.mark.skip decorators from gradient flow tests
- Convert environment validation skips to warnings for optional checks
- Change milestone tests from skip to fail when scripts missing
Tests now either pass or fail - no silent skipping that hides issues.
This ensures the test suite provides accurate feedback about what works.