Thanks Tooseevee and Bmadd34! You were indeed both correct. Now the handlebar light switch works as it ought, which is to say, with the ignition switch on the two little parking marker lights on the nacelle and the taillamp light up on the "P<" (Parking) setting, stay on with the full lights setting (with the headlamp icon), but the headlamp does not shine until the motor's running. So, I guess all is as it should be. Barring some need or wish to run dark, I'll likely just leave the switch set on full lights, so I don't forget them, and all should be pretty much as it was before.
I had sort of expected that my Ammeter might return to that traditional start up routine behavior of flicking a smidgeon left and then right-to-center again near TDC, as the points opened and closed, which I had assumed was being masked by the big draw of the always-on headlamp, but a previous owner had splurged on an electronic ignition (for which I am grateful), so there's no difference there. That's OK...I'm now long since used to finding "TDC and a tad" without the Ammeter's help anyhow.
Thanks again guys!