A little update. I threw on a couple of wheels (mismatched and not destined for this bike) and an old MTB seat to check the static geometry -- feels pretty good. I like the looks of the bike.
With the seat and wheels on, I was able to move the seat post a few mm after a couple of hours of PB Blaster soaking in. I added a more PB Blaster, wiggled it a few times, and I'll let it sit overnight and check it again tomorrow.
I also took apart the headset. Bianchigirl was correct, it was pretty obvious that the headset it shot. Really really shot.
Since it's a 1" steerer tube, I'm temped to go threadless, but I've already ordered an CF aero dropbar that needs the modern 31.8mm clamp area. I've done a bit of research, and this wrecked headset was apparently Cane Creeks bottom of the line Aheadset. I've read that Cane Creek Forty headsets are good value, but require specific tools or a professional install. Suggestions on moderately priced 1" headsets that I might consider installing myself?