Function prepare_input_owned 

pub fn prepare_input_owned<T>(
    arr: StridedArray<T>,
    n_group1: usize,
    n_group2: usize,
    conj: bool,
    requires_unit_stride: bool,
    use_pool: bool,
    materialize_conj_fn: Option<fn(T) -> T>,
) -> Result<ContiguousOperand<T>, EinsumError>
where
    T: ScalarBase + 'static,

Prepare an owned input array for GEMM.

Expects batch-last canonical order: [group1..., group2..., batch...]. If already contiguous after dimension grouping, transfers ownership without copying. Otherwise, copies to a new col-major buffer.

Parameters are the same as prepare_input_view.