As I noted, I had overwritten my bootloader with non functional code. Having uploaded and let everyone else test the loader, it was time for me to do it, too. To do this, I needed to put the board into serial loader mode so the ST-Link would have time to get ahold of the chip.
To do that, I pulled Boot0 high (connected it to the +3.3v from the ST-Link, which I'm using to power the board), and Boot1 Low (connected it to the middle pin on a sensor port.
I was immediately able to reset the chip, flash the lerdge base bootloader on, and get my beautiful "NO APP" Error message.
This is 100% expected - after a reflash, there's no app on the board. If you wanted to move back to Lerdge's firmware, you'd proceed with a normal force update mode.