TRCC: T-Regulated Cytokine Clustering

TRCC is a density-peak clustering algorithm that combines a kNN-truncated Gaussian density estimator with a path-density mutual-reachability merge condition. The reference implementation provides a sub-quadratic kd-tree C++ extension (via pybind11 and nanoflann) and a bit-identical pure-Python fallback, an sklearn-compatible API, a 37-dataset benchmark harness, and Optuna-based hyperparameter tuning.