Add the exact dataset_stats.json used by the RoboCOIN FastWAM and FastWAM-Joint training runs. The mixed dataset contains 342 episodes and 238864 transitions across object classification, test-tube mixing, and basket stacking, using the Galaxea millimetre gripper convention. Source SHA256: b3bc2d0d090e84ef78ace8c4388d517b53a8bc01a5ea95a82b0cf9a5f42cf41a