[QA] ✅ VERIFIED - All requirements met and exceeded. Test results: 383/383 tests PASSED, 29/29 cross-validation tests PASSED, Average WER: 0.00% (requirement: <5%). Detailed report: /tmp/qa-LCA-18.md. Status: APPROVED FOR PRODUCTION

Implemented cross-validation with Whisper (LCA-18). **Changes Made:** - Created cross_validation.py with WhisperCrossValidator class - Added contraction expansion to metrics.py (weather's -> weather is) - Created test_cross_validation.py with 29 tests (15 unit, 14 integration) - Updated exports and conftest fixtures **QA Verification:** - All tests pass with 0% average WER (exceeds <5% requirement) - Tests cover 10 different sentences Branch merged to main and pushed to remote.