How do I suppress the whitespace above an equation block at the page top?

It is not a skip that you have above the equation but a one line paragraph consisting of an indentation box and parfillskip glue. TeX display math environments do not generally react well to starting a paragraph they are designed to work mid-paragraph. If you need to do this you need to suppress the paragraph start with

\noindent
\begin{equation*}

and you will see the equation move up the page.