NwcIO v0.1.1

Security & Clean-Room Governance

• Strict Clean-Room Policy: Full abstraction of external test fixtures via NWCIO_TEST_FILES environment variable and optional uncommitted test_files/ directory, mirroring the RvtIO standard.
• Fixture Resolution Helper: Introduced TestFiles helper class in NwcIO.Tests with zero hardcoded filesystem paths or machine-specific fallback directories.
• Documentation: Added docs/test-fixtures.md documenting clean-room testing principles, test skipping rules, and fixture expectations.
• Anonymized Benchmarks: Scrubbed all specific project references, real industrial facility names, and local test model filenames from README, format notes, and tests.