Decode a r32uint sample from the picker target.
Express id when bit 30 is set (GPU-instanced occurrence); 0 otherwise.
Convenience: which discipline produced the hit.
Mesh index (1-based) when bits 30-31 clear and value > 0; 0 = no hit.
Federated expressId when bit 31 is set; 0 otherwise.
Decode a r32uint sample from the picker target.