model Descriptor
Constructs a data class that describes the model's current configuration.
The returned ModelDescriptor captures all three control families (numeric, string, and JSON) via ksl.controls.Controls.exportAll, along with the model's intrinsic run-parameter defaults (via ksl.controls.experiments.ExperimentRunDefaults), random variable parameter data, and response names.
Runtime-identification values (experimentName, experimentId, runName) are deliberately omitted from the descriptor — they identify a particular run rather than the model itself, and including them would make the descriptor JSON vary byte-for-byte across builds for reasons unrelated to model content.
Return
the model descriptor at the time of the call