flasher works again :D Debugging it was greatly helped by having labeled my pin wires.
I was looking into the firmware and discovered it had a debugging mode that opened an interactive terminal. I added a command to the terminal source to send test values on the various pins, outputting text describing where each logic level should end up. I found one of my wires was miswired and mislabeled in a hard-to-notice way. Maybe I rewired it wrongly after it fell out or something. I tested and verified each voltage level, ignoring logic flow. Annnd now it works! Now to clean things up and use it again. Topic _seems_ resolved. Ideally I contribute code successfully to coreboot, a larger goal. In the meantime, I found a local makerspace and started a radio tool.
