Well, I have a preliminary finding which only proves that I am an idiot.
I swapped bearings as I couldn't find a spoke loose. That didn't help. I inspected and tinkered to no avail. Brakes not an issue.
Finally, last night, in readying to bring to the LBS for their inspection, I decided to swap tires and tubes. And viola!, the sound goes away.
What I am deducing is that the inner tube I was using I had patched. So, when the tube was fully inflated there is a gap between the tube and tire in the area of the patch.
Anyone ever hear of that making a clicking sound? I have patched many a tube and never encountered it.
I tested last night with a different tube tire combo and it appears the click is gone, but I only rode around the block a few times. Will test on a long ride this weekend.