chore: 降低 list_todos 日志级别为 debug

前端每次 todo_write 后自动刷新会触发 list_todos 命令，子代理多次更新待办时产生大量 INFO 日志噪音。将 handler 与 gateway 转发两处日志降级为 debug，默认不输出，需要排查时通过 RUST_LOG=debug 开启。

src/command/handlers/list_todos.rs

@@ -64,7 +64,7 @@ impl CommandHandler for ListTodosCommandHandler {
             .list_todos(&scope_key)
             .map_err(|e| CommandError::new("LIST_TODOS_ERROR", e.to_string()))?;
 
-        tracing::info!(
+        tracing::debug!(
             scope_key = %scope_key,
             record_count = records.len(),
             "list_todos handler: reading from store"

src/gateway/ws.rs

@@ -676,7 +676,7 @@ async fn handle_inbound(
                             .get("todos_scope_key")
                             .cloned()
                             .unwrap_or_default();
-                        tracing::info!(todo_count = todos.len(), %scope_key, "list_todos command response");
+                        tracing::debug!(todo_count = todos.len(), %scope_key, "list_todos command response");
                         let _ = sender.send(WsOutbound::TodoList { todos, scope_key }).await;
                     }
                 }