input-protocol -> library/protocol/input/input-protocol.zig. Its five
consumers (usb-hid keyboard/mouse, ps2 keyboard/mouse, the input service) now
import the module directly and alias it input_protocol, replacing the
runtime.input_protocol re-export (deleted) and the inconsistent local `protocol`
aliases. runtime.input (the client) still imports the module by name.
zig build + test green; input, acpi-ps2, usb-hid pass.
Daniel Samson