chore: 修复 clippy error（loop never loops → if-let）并应用自动修复

src/channel/client.rs

@@ -335,15 +335,14 @@ impl WeChatClient {
             .map_err(|e| format!("解析发送响应失败: {}", e))?;
 
         // 校验业务返回码（存在 ret 字段且非 0 才算失败）
-        if let Some(ret) = resp.get("ret").and_then(|v| v.as_i64()) {
-            if ret != 0 {
+        if let Some(ret) = resp.get("ret").and_then(|v| v.as_i64())
+            && ret != 0 {
                 let errmsg = resp.get("errmsg").and_then(|v| v.as_str());
                 return Err(format!(
                     "发送消息业务失败 ret={} errmsg={:?}",
                     ret, errmsg
                 ));
             }
-        }
 
         Ok(client_id)
     }

src/channel/types.rs

@@ -118,6 +118,7 @@ pub struct RefMessage {
 
 /// 消息条目（支持 text/image/voice/file/video）
 #[derive(Debug, Clone, Serialize, Deserialize)]
+#[derive(Default)]
 pub struct MessageItem {
     #[serde(rename = "type", skip_serializing_if = "Option::is_none")]
     pub item_type: Option<i32>,
@@ -165,27 +166,11 @@ impl MessageItem {
     }
 }
 
-impl Default for MessageItem {
-    fn default() -> Self {
-        Self {
-            item_type: None,
-            create_time_ms: None,
-            update_time_ms: None,
-            is_completed: None,
-            msg_id: None,
-            ref_msg: None,
-            text_item: None,
-            image_item: None,
-            voice_item: None,
-            file_item: None,
-            video_item: None,
-        }
-    }
-}
 
 // ─── 微信消息 ───
 
 #[derive(Debug, Clone, Serialize, Deserialize)]
+#[derive(Default)]
 pub struct WeixinMessage {
     #[serde(skip_serializing_if = "Option::is_none")]
     pub seq: Option<i64>,
@@ -217,26 +202,6 @@ pub struct WeixinMessage {
     pub context_token: Option<String>,
 }
 
-impl Default for WeixinMessage {
-    fn default() -> Self {
-        Self {
-            seq: None,
-            message_id: None,
-            from_user_id: None,
-            to_user_id: None,
-            client_id: None,
-            create_time_ms: None,
-            update_time_ms: None,
-            delete_time_ms: None,
-            session_id: None,
-            group_id: None,
-            msg_type: None,
-            message_state: None,
-            item_list: None,
-            context_token: None,
-        }
-    }
-}
 
 impl WeixinMessage {
     #[allow(dead_code)]