e6d77650f7
Combine sparse vectors in-place by first counting total `nnz` and then working backwards from the end. This removes the need for temporary buffers in `mju_combineSparse` and its callers and speeds up the function by ~10%. PiperOrigin-RevId: 902530210 Change-Id: I4f48c327103552ab968d3915399c6067367bec9f