README: Fill Quality section (core optimization target, metrics, reward
function, PerformanceMatrix, CMA-ES integration)
HftBacktestCWM integration doc: FillQuality dataclass, fill_value_score
computation, reward function weighting, PerformanceMatrix tracking
OB microstructure study: Section 13 — Fill Quality Optimization,
per-asset expectations, optimization strategy, connection to OB dynamics
Fill quality is MALKHUT's core aim: the system learns to get better fills
(faster, better-priced, less adverse selection) across regimes and venues.