Let \( z=a+ib ,\; b\neq 0 \) be complex numbers satisfying \( z^{2}=\overline{z}\cdot 2^{\,1-|z|} \). Then the least value of \( n\in\mathbb{N} \), such that \( z^{n}=(z+1)^{n} \), is equal to _______________.