ObjectState reconstructs concrete nested subtypes through their base annotation #16

ObjectState flattens fields from the actual nested dataclass value but records its annotation type as the reconstruction owner, except for registered lazy dataclasses. A concrete subtype therefore contributes extra fields that its base annotation cannot accept.

OpenHCS original 3D CellProfiler configuration has VolumeSourceSpatialDomain in a field annotated SourceSpatialDomain. After the independent context merge fix (#14/#15), constructing ObjectState(config) fails in _reconstruct_from_parameter_snapshot with SourceSpatialDomain.__init__() got an unexpected keyword argument source_depth. This is the actual compiler configuration boundary, not a missing image declaration or a wire fallback.

The existing flattened parameter type index should retain the actual dataclass owner for concrete nominal subtypes as well as lazy values, so raw, live-resolved and saved-resolved reconstruction consume the same schema that was flattened. Replacement with a different nominal subtype must rebuild the existing parameter topology.