refactor(events): 将设备状态广播降级为快照同步并按需订阅 WebSocket 事件，顺带修复相关测试

src/atx/mod.rs

@@ -93,11 +93,7 @@ mod tests {
 
     #[test]
     fn test_discover_devices() {
-        let devices = discover_devices();
-        // Just verify the function runs without error
-        assert!(devices.gpio_chips.len() >= 0);
-        assert!(devices.usb_relays.len() >= 0);
-        assert!(devices.serial_ports.len() >= 0);
+        let _devices = discover_devices();
     }
 
     #[test]