Each record now starts with an i64 timestamp (nanoseconds since epoch)
before the feature/target/OFI data. v1 records grow from 432 to 440
bytes, v2 from 112 to 120 bytes. The timestamp is always i64 even in
bf16 mode. train_baseline_rl reconstructs bars with real timestamps
instead of placeholders so the walk-forward windower can split by month.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>