Meanwhile, in a smoky apartment on the bad side of town[1]:
Warning: this hard locked my MBP. [snip] It was a pain in the ass to recover: my only option seemed to be to power down and power back up again, at which point OSX helpfully remembered the state my machine was in and dropped me back into the blacked-out display and maxed fan. Some combination of NVRAM reset, SPC reset and safe mode was required to get back in.