I found the source of the problem: the Windhawk mod "Fix Darkmode ListViews".
I followed these steps for a clean boot. Once Windows started. I opened AutoRuns and the dark mode looked correct (light text, dark background). I remembered that Windhawk has occasionally caused issues for me, so I started WindHawk and then re-opened AutoRuns. As I expected, the problem returned. I disabled "Fix Darkmode ListViews" and tried again. The problem was gone. I have since added Autoruns64.exe and Autoruns.exe to Windhawk's list of excluded processes and disabled that mod.
EDIT: Since I answered my own question, I'm linking to this article about self-answering questions as per Microsoft Q&A guidelines.