Model type is irrelevant during data collection. Models are now created lazily on first use: train_model() creates a ReactorDynamicsModel, fit_knn(k) creates a ReactorKNNModel. load_model() detects type by file extension as before. drop_well_fitted() now checks model exists. Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>