A self test, a startup sound and a splash screen

Audio is now working both ways, verified by a self test that plays and records sounds simultaneously. Testing the two paths together rather than one at a time is the only version of that test worth having, because a capture path that only works while nothing is playing is exactly the failure a call would hit.

By extension that gives the ability to play a startup sound.

It is not too annoying. It observes quiet hours, and it also observes the state of the mute key, which appears to be implemented in hardware. A machine that ignores the mute key and then sings at you at six in the morning is a machine nobody wants, and the check costs nothing.

It is also a small amount of work to add a splash logo on boot, so that is in too. A little more polish, and neither of these is load-bearing, but a machine that boots to a logo and a chime feels finished in a way that a machine that boots to a serial log does not.