InsideForestRegressor (deprecated)

Use InsideForestContinuousRegionClusterer in new code. This compatibility name emits FutureWarning, accepts historical parameters, temporarily keeps forest R² as score, and is scheduled for removal in 0.5.0.

The canonical class returns region IDs, explicit -1 for unmatched rows, and η² from score. Parameters method, n_clusters, include_summary_cluster, divide, and balance_clusters are accepted only for migration.