oops...figured it out
Ummm, first I have to just cough up the fact that I'm an idiot. It seems that it was my brain, not my headlight, was malfunctioning.
But to my credit, tonight was the first time I've ridden the bike at night since discovering the "malfunction." I learned tonight that the main low-beam bulb doesn't light until you actually fire the bike up, not just turn the key on. It works just fine. Explains the lack of a warning indicator on the instrument panel, too.
I knew it would eventually happen. My motorcycle is officially smarter than me.