Load a single MJ: ML Models row by id, fully typed for mutation-free reads.
model primary-key value
OptionalcontextUser: UserInforequest user — required server-side for isolation/audit
Optionalprovider: IMetadataProvideroptional provider for multi-provider correctness
RunView-backed IMLModelLoader. Loads the model as a fullentity_object(it is read for its frozen contract, not mutated) and returnsnullwhen not found.