feat(input-server): add InputServer<D: InputDevice> with protocol, mock + UART adapters, and tests

crates/servers/input-server/src/input_device.rs

@@ -0,0 +1,6 @@
+use crate::protocol::InputEvent;
+
+pub trait InputDevice {
+    fn poll(&mut self) -> Option<InputEvent>;
+    fn has_event(&self) -> bool;
+}