v0.3 – CSS-Ready BP Engine

LiDMaS+ v0.3 introduces a CSS-ready decoding architecture built on the validated LDPC belief propagation engine.

New:
• CSSCode abstraction (Hx, Hz support)
• Dual BP decoding for X and Z channels
• Logical operator scaffolding
• Clean separation between classical and quantum layers

Core classical engine remains validated:
• Monotonic FER waterfall
• Sum-product and normalized min-sum
• LLR clipping and convergence controls
• OpenMP Monte Carlo benchmarking

This release establishes the foundation for quantum error correction simulations (CSS → surface codes → CV QEC).