Change PercentileScaler, RewardNormalizer, CompositeReward, and
PPORewardShaper public APIs from f64 to f32 — matching what callers
actually pass. Internal EMA/percentile math stays f64 for precision.
Keep data_loader SMA/EMA/MACD accumulators in f64 throughout (was
f64→f32→f64 per step), cast to f32 only at output boundary.
Remove dead _transition computation in rainbow_agent_impl and unused
bigdecimal deps from broker_gateway_service and trading_service.
2704 tests pass, 0 clippy warnings.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>