The QMP harness channel, the SCI + power button published from ring 3,
Notify/GPE dispatch in the AML interpreter, and orderly shutdown — init's
M17 stop cascade into a ring-3 S5 write. Proven by injecting a real ACPI
power-button event; QEMU powers off through the whole chain.
# Conflicts:
# system/services/init/init.zig