Some sort of divine intervention answered my panicked cry for help by disabling my laptop soon after I posted this. It had just finished a backup when it went into some sort of “kernel task” CPU overdrive which stopped the battery charging and now it refuses to turn on. (2018 MacBook Pro - it exhibited this symptom when I first got it so I’m pretty sure that the worst case scenario is a trip to the Apple Store and a little time to work on things away from the computer). Fingers crossed it miraculously recovers tomorrow morning