新增: df-relay Phase2 WS中继实现(Hello握手+鉴权+ConnRegistry配对路由+Event/Command方向分发)

crates/df-relay/src/error.rs

@@ -20,7 +20,7 @@ pub enum RelayError {
     #[error("广播失败: {0}")]
     Broadcast(String),
 
-    /// WS 协议层错误(底层 tungstenite)
+    /// WS 协议层错误(底层 axum::extract::ws / tungstenite)
     #[error("WS 协议错误: {0}")]
     WebSocket(String),
 
@@ -28,6 +28,10 @@ pub enum RelayError {
     #[error("消息序列化失败: {0}")]
     Serde(#[from] serde_json::Error),
 
+    /// 广播发送失败(mpsc channel 对端已断开)
+    #[error("广播 channel 发送失败: {0}")]
+    Channel(String),
+
     /// 其他未归类错误(降级通道)
     #[error("中继内部错误: {0}")]
     Other(#[from] anyhow::Error),