结构调整，便于后续扩展

AIStudio.Wpf.Flowchart/NodeKinds.cs

@@ -0,0 +1,22 @@
+using System.ComponentModel;
+
+namespace AIStudio.Wpf.Flowchart
+{
+    public enum NodeKinds
+    {
+        [Description("节点")]
+        Normal = 0,
+        [Description("开始")]
+        Start = 1,
+        [Description("结束")]
+        End = 2,
+        [Description("中间节点")]
+        Middle = 3,
+        [Description("条件节点")]
+        Decide = 4,
+        [Description("并行开始")]
+        COBegin = 5,
+        [Description("并行结束")]
+        COEnd = 6,
+    }
+}