forked from 1b-agent/fieldcraft-upstream
nl-hybrid-incompressible: 27 hybrid hex8 at ν = 0.4999 pulled to λ = 2 by a prescribed displacement, against the compressible neo-Hookean closed form (1.4·10⁻⁹); its first iterations need the LDLᵀ factorization. ROADMAP and parity updated, docs/oracle.md regenerated. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>