Check out this video! It's working!!
I assembled the wee PCB Sunday night, but it had an odd behavior, never turning on at all during the "flashing on and off" portion of the code. My first guess was that it had something to do with the 47kΩ and 68kΩ resistors that I used instead of the expected 4.7kΩ and 7.5kΩ, but the TLVH knowledge base suggests that shouldn't change anything except at particularly low currents. In my shower thoughts today I realized it could be the pin that I'm using for ADC measurements. The pseudorandomness of the flicker comes from taking multiple consecutive ADC readings on floating pin, and only keeping the least significant bit each time. Maybe a solder blob under the chip was influencing the ADC readings? So I switched to the one remaining spare pin for ADC readings and IT TOTALLY WORKED NO OTHER ISSUES yessssssssssss
The git repo is updated. I still want to tweak the animation a little more before I cut the LED loose from the programming jig.