连线时能否像飞书一样，鼠标移到边界自动移动画布

### 功能描述

在流程图比较大的时候，往往需要对两个距离比较远的节点进行连线，缩小了又不好连线，放大了又不能同时看到这两个节点

### 期望解决方案

连线时能否像飞书一样，鼠标移到边界自动移动画布

Start by locating the connection interaction and canvas viewport/panning entry points, then reproduce the large-diagram case described in the issue. Done means moving the pointer to a canvas boundary while connecting automatically pans the canvas, allowing distant nodes to be connected without repeatedly zooming.

Written by the indexing model from the issue text.