Replace all `.to_string().parse::<f32/f64>()` patterns with
`num_traits::ToPrimitive` methods (`.to_f32()`, `.to_f64()`).
Each string roundtrip heap-allocated per conversion — fatal in
DQN hot loop (300K+ bars × epochs). Decimal stays as canonical
financial type; conversions happen at GPU/float boundaries only.
Also fixes blocking_read() in async context (risk_integration.rs).
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
- Created data/examples/download_ml_training_data.rs using reqwest + Databento HTTP API
- Downloaded 90 days × 4 symbols (ES.FUT, NQ.FUT, ZN.FUT, 6E.FUT)
- Files saved to test_data/real/databento/ml_training/
- Total: 360 files, 15 MB compressed DBN format
- Used existing Rust pattern from download_nq_fut.rs
- API key loaded from .env file
- 100% success rate (360/360 files)
- Ready for ML training benchmarks
Next: Create simplified training benchmark for RTX 3050 Ti GPU measurements