Deprecated river.neural_net; importing it now emits a DeprecationWarning and users are encouraged to use deep-river for neural networks. Addresses #1828.
Fixed MondrianNodeClassifier.replant not copying the counts attribute when promoting a leaf to a branch, leaving the new branch with n_samples != 0 but empty class counts. The fix mirrors the regressor's _mean copy and matches the reference onelearn implementation. Addresses #1823.