Add cell-3 reach-task demonstrations to BusyBox multitask (part 2)

Add cell-3 reach-task demonstrations to BusyBox multitask

Merge cell-3 demonstrations into single-arm BusyBox multitask (part 2)

Merge cell-3 demonstrations into single-arm BusyBox multitask

Fix LeRobot dataset visualization link

Recompute merged numeric statistics after index remapping

Publish single-arm BusyBox multitask dataset

initial commit