generate_report wrote train_data.csv and test_data.csv with index=False, which
dropped the UTC time index. laborious drift reads test_data.csv from MLflow as
its reference and needs a timestamp column; without it, every model trained here
drifted against the first 30% of its own target window. Both CSVs now write the
index as timestamp. If a column already has that name, the CSV is written as
before and a warning is logged, so training never fails over drift.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
37f16f34ff