Core YAML-to-callable system compiler

[jc-macdonald]

Port the core system specification compiler from ACCIDDA/op_system to Julia.

Scope (package only)

• Parse YAML system definitions via YAML.jl
• Define Julia types: SystemSpec, StateVariable, Parameter, OperatorPartition
• Compile YAML → callable ODEFunction compatible with DifferentialEquations.jl
• Support operator partitioning: split RHS into reaction, diffusion, advection terms
• Axis specification: declare trait, spatial, and structured axes with bounds and resolution
• Parameter injection: named parameter sets that map to system coefficients
• Validation: check axis compatibility, parameter completeness, operator dimensions

Boundary

This package produces a compiled system spec. The solver lives in OpEngine.jl. The evaluation lives in ModelCriticism.jl.