Fix DataFrame predict(_proba) compatibility (AutoGluon wrappers)

[oegedijk]

Summary

• fix classifier helper paths that indexed raw predict_proba outputs before coercion
• fix regression helper path that indexed raw predict outputs before coercion
• coerce one-vs-all scorer predict_proba output to numpy before slicing
• add regression tests for DataFrame-returning predict_proba and predict
• update release notes and remove Autogluon and explainerdashboard integration #270 from TODO Next list

Why

Some model wrappers (including AutoGluon-style wrappers) return pandas DataFrame outputs from predict_proba/predict. Existing tuple/integer indexing on raw outputs caused InvalidIndexError/KeyError in these paths.

Tests

• uv run pytest tests/test_classifier_base.py -k "test_prediction_result_df or dataframe_predict_proba or test_permutation_importances" -q
• uv run pytest tests/test_dtype_alignment.py -k dataframe_predict_proba -q
• uv run pytest tests/test_regression_base.py -k "dataframe_predict or test_prediction_result_df or test_preds or test_permutation_importances" -q

Fixes #270