So I've found that scene.create snapshots don't persist across restarts of HA, and that this is intentional. Alright.
But turning lights off and back on as they were (and reliably so) based on presence detection strikes me as a, if not the, fundamental home automation task.
How do you all achieve this? Clearly I must be missing something. (I've also raised this over on the forums, just polling for ideas here as well.)