New 362-line material cache system:
- GlobalMaterialCache{StateType}: stores state variables at all IPs/elements
- material_state_type(): infer state NamedTuple type from material traits
- create_global_material_cache(): factory function with automatic type inference
- create_zero_state(): zero-initialize state NamedTuples
- Supports stateless (empty NamedTuple) and stateful materials
- Type-stable NamedTuple-based storage
- Zero-allocation state updates (functional style)
- Already integrated in JuliaFEM.jl (line 437)
Provides persistent state storage for time-stepping and material state management.
Jukka Aho