Well, I flattened the "hold down plate", reinstalled the adjuster wheel the correct orientation, sewed it all back up and adjusted the parking brake per the shop manual.  The noise is gone.  I'm going to keep my fingers crossed that it stays gone, but that "hold down plate" was kinda chewed.  And you can't replace it without dismantling the entire hub assembly.  I hope it was just the fact that the adjuster was incorrectly installed that caused all the hubbub in the first place and that its fixed now.  The other possibilities are that the retention springs are weak or the backing plate is bent or something else that I didn't see, but essentially, that front shoe was kinda flopping around inside the hub and hitting the anchor pin once per revolution.  How that was precipitated by applying the disk brake still eludes me.  There was no evidence of the shoe ever hitting the studs on the back of the hub.  But it did seem that it wouldn't make the noise until the brakes had warmed up.  I dunno, it still just doesn't make any sense.