Solution (source code)

= Solution

Since $s$ is <proper time>, the <four-acceleration> is
$$
A=\frac{dU}{ds}=c\omega(\sinh\omega s,\cosh\omega s,0,0).
$$
Its <Minkowski norm> squared is $g(A,A)=-c^2\omega^2$, so the invariant magnitude of <proper acceleration> is
$$
\boxed{\sqrt{-g(A,A)}=c\omega.}
$$
The vector is spacelike, which accounts for the minus sign under the square root.