[hmgaudecker]

What changes

• build_model_spec(...) returns the model's domain as keyword arguments for lcm.Model:
  • regimes, ages and regime ids;
  • description and derived categoricals;
  • the default entry initial_nodes;
  • edges and the broadcast functions, constraints, states and transitions.
• One builder covers both models: policy=None builds the baseline, and a PolicyVariant applies its ACA overlay. The ACA factory module is removed.
• The spec builder takes pia_aime_grid instead of fixed_params. pia_aime_grid is the only parameter that grid construction reads. build_grids, build_all_regimes and build_model_slots take it the same way.
• create_model(spec=..., fixed_params=..., **model_options) forwards every other lcm.Model option unchanged. An option the spec also holds, such as initial_nodes, overrides the spec's value. create_model does not trim or rewrite the params.
• aca-model no longer supplies an execution-config default. Without execution_config, pylcm's "device" budget applies. That budget needs a preallocated allocator pool, which every Marvin batch job already has through the workspace slurm_env.
• create_benchmark_model(*, pref_type_grid, grid_config, final_age, **model_options) builds through the same spec.
• Tests:
  • the spec holds exactly the domain keys;
  • a missing execution config is not filled in;
  • an explicit config, an arbitrary option (durable_identity) and an initial_nodes override all reach Model unchanged.
• The README is updated.

https://claude.ai/code/session_01Hs8mfXPYyEa24KaAp6BwCW