Solution (source code)

= Solution

Multiply the <eigenvalue equation> $Ax=\lambda x$ on the left by $x^\dagger$. The <unit vector> normalization is $x^\dagger x=1$, so
$$
\boxed{\lambda=x^\dagger Ax=x^\dagger Hx+i\,x^\dagger Sx.}
$$
No <normal matrix> assumption on $A$ is needed: this is an identity for each normalized eigenvector.