Module clustering 

Shared spatial-hash clustering with union-find.

Used by the obstacle detector, scene graph builder, and perception pipeline to avoid duplicating the same algorithm.

Optimizations

• Union-by-rank prevents tree degeneration, keeping find near O(α(n)).
• Path halving in find for efficient path compression.
• #[inline] on hot helpers to ensure inlining in tight loops.

Functions

cluster_point_cloud

Cluster a point cloud using spatial hashing and union-find over adjacent cells.