Remove nturgbd120/test.csv — NTU RGB+D 120 restricted from redistribution per ROSE Lab agreement

Remove nturgbd120/validation.csv — NTU RGB+D 120 restricted from redistribution per ROSE Lab agreement

Remove nturgbd120/train.csv — NTU RGB+D 120 restricted from redistribution per ROSE Lab agreement

Remove nturgbd120 config from public release (NTU RGB+D 120 redistribution restriction)

docs: clarify HMDB51 (NC) and NTU RGB+D 120 (redistribution restriction) license notes

Add FSOS-AR benchmark splits (Diving48, HMDB51, NTURGBD120, SSv2, UCF101)

initial commit