power-protocol -> library/protocol/power/power-protocol.zig. Its two consumers
(init and the acpi discovery service) import it directly; the
runtime.power_protocol re-export and the runtime module import are dropped (no
runtime client speaks it). The now-empty system/services/power/ is removed.
This completes library/protocol/: every driver<->service wire contract lives
there and is imported by module name, no protocol is re-exported through
runtime, and the alias chaos (dp/sp, mixed protocol/<x>_protocol) is resolved.
virtio-gpu-protocol stays a driver-private relative import (a hardware command
set, not a driver<->service seam — like virtio-pci.zig beside it).
zig build + test green; power-button, orderly-shutdown pass.