Pass configs via dependency injection into model classes (BaseModelConfig-only; dict supported)

[cpaniaguam]

Base branch

Implementation work for this issue on: rlssm-class-make-model-dist.

Philosophy / non-negotiables

• The authoritative config object used by any model instance MUST be a subtype of
  BaseModelConfig (e.g., Config, RLSSMConfig, and future family configs).
• Users MAY pass a dict for configuration (project decision), but dict must be
  treated as an input convenience only:
  • normalize/coerce the dict into the appropriate BaseModelConfig subtype ASAP,
  • validate it,
  • and then store/use only the typed config object for the remainder of model construction.

What should change

1) Move build policy into config families

Each model-family config class must implement its own _build_model_config(...)
(family-specific builder), rather than relying on one centralized builder in HSSMBase.

The family builder is responsible for:

• resolving defaults (from_defaults(...)),
• normalizing user overrides provided as dict into the family config type,
• resolving precedence rules (e.g., choices= argument vs config-provided choices),
• and returning the final, validated config object (still a BaseModelConfig subtype).

2) Model instances must keep config state

Each model instance must keep a reference to the exact config object used to build it
(e.g., self.model_config: BaseModelConfig or similar), and distribution-building should
read from that object consistently.

Avoid having the “true config” split between:

• self.model_config and a separate set of copied scalar attributes,
  except where absolutely required for backwards compatibility.

Dict compatibility requirement

The DI refactor must preserve the ability to pass config overrides as a dict, but the
dict must be normalized into a BaseModelConfig subtype before use.

Code references (current state)

• Config family hierarchy:
  • https://github.com/lnccbrown/HSSM/blob/cd660da092b4ea9d2cd9fed684495259421d4fe4/src/hssm/config.py
• Current centralized builder to refactor away from:
  • https://github.com/lnccbrown/HSSM/blob/26a933675fedbda29eb6920b4c99a75cf80245ed/src/hssm/base.py
• RLSSM already follows DI-style patterns (config injected + Op constructed externally):
  • https://github.com/lnccbrown/HSSM/blob/26a933675fedbda29eb6920b4c99a75cf80245ed/src/hssm/rl/rlssm.py