feat(workflow): add floating directed edges

frontend/src/components/workflow/ConditionEdge.tsx

@@ -8,7 +8,10 @@ import {
   BaseEdge,
   EdgeLabelRenderer,
   getBezierPath,
+  Position,
   type EdgeProps,
+  type InternalNode,
+  useInternalNode,
 } from "@xyflow/react";
 import { Trash2 } from "lucide-react";
 import { useContext } from "react";
@@ -16,8 +19,77 @@ import { useContext } from "react";
 import { cn } from "@/lib/utils";
 import { EdgeActionContext } from "./context";
 
+type EdgeEndpoint = {
+  x: number;
+  y: number;
+  position: Position;
+};
+
+function getNodeCenter(node: InternalNode) {
+  const width = node.measured.width ?? node.width ?? 0;
+  const height = node.measured.height ?? node.height ?? 0;
+
+  return {
+    x: node.internals.positionAbsolute.x + width / 2,
+    y: node.internals.positionAbsolute.y + height / 2,
+    width,
+    height,
+  };
+}
+
+/**
+ * 计算一条从节点中心朝外的射线与节点矩形边界的交点。
+ * 这样边只依赖节点的位置和尺寸，不会被创建连接时使用的底部 Handle 限制。
+ */
+function getNodeBoundaryPoint(
+  node: InternalNode,
+  direction: { x: number; y: number },
+  fallbackPosition: Position,
+): EdgeEndpoint | null {
+  const center = getNodeCenter(node);
+  if (!center.width || !center.height) return null;
+
+  const { x: dx } = direction;
+  let { y: dy } = direction;
+  if (dx === 0 && dy === 0) {
+    dy = fallbackPosition === Position.Top ? -1 : 1;
+  }
+
+  const halfWidth = center.width / 2;
+  const halfHeight = center.height / 2;
+  const normalizedX = dx / halfWidth;
+  const normalizedY = dy / halfHeight;
+  const scale = 1 / Math.max(Math.abs(normalizedX), Math.abs(normalizedY));
+  const hitsVerticalSide = Math.abs(normalizedX) > Math.abs(normalizedY);
+
+  if (hitsVerticalSide) {
+    // 避开圆角，让吸附点始终落在可见的直边上。
+    const cornerInset = Math.min(16, halfHeight);
+    return {
+      x: center.x + dx * scale,
+      y: Math.min(
+        center.y + halfHeight - cornerInset,
+        Math.max(center.y - halfHeight + cornerInset, center.y + dy * scale),
+      ),
+      position: dx > 0 ? Position.Right : Position.Left,
+    };
+  }
+
+  const cornerInset = Math.min(16, halfWidth);
+  return {
+    x: Math.min(
+      center.x + halfWidth - cornerInset,
+      Math.max(center.x - halfWidth + cornerInset, center.x + dx * scale),
+    ),
+    y: center.y + dy * scale,
+    position: dy > 0 ? Position.Bottom : Position.Top,
+  };
+}
+
 export function ConditionEdge({
   id,
+  source,
+  target,
   sourceX,
   sourceY,
   targetX,
@@ -26,16 +98,42 @@ export function ConditionEdge({
   targetPosition,
   data,
   selected,
+  markerEnd,
 }: EdgeProps) {
   const actions = useContext(EdgeActionContext);
+  const sourceNode = useInternalNode(source);
+  const targetNode = useInternalNode(target);
+
+  const sourceCenter = sourceNode ? getNodeCenter(sourceNode) : null;
+  const targetCenter = targetNode ? getNodeCenter(targetNode) : null;
+  const sourceEndpoint = sourceNode && sourceCenter && targetCenter
+    ? getNodeBoundaryPoint(
+        sourceNode,
+        {
+          x: targetCenter.x - sourceCenter.x,
+          y: targetCenter.y - sourceCenter.y,
+        },
+        Position.Bottom,
+      )
+    : null;
+  const targetEndpoint = targetNode && targetCenter && sourceCenter
+    ? getNodeBoundaryPoint(
+        targetNode,
+        {
+          x: sourceCenter.x - targetCenter.x,
+          y: sourceCenter.y - targetCenter.y,
+        },
+        Position.Top,
+      )
+    : null;
 
   const [path, labelX, labelY] = getBezierPath({
-    sourceX,
-    sourceY,
-    sourcePosition,
-    targetX,
-    targetY,
-    targetPosition,
+    sourceX: sourceEndpoint?.x ?? sourceX,
+    sourceY: sourceEndpoint?.y ?? sourceY,
+    sourcePosition: sourceEndpoint?.position ?? sourcePosition,
+    targetX: targetEndpoint?.x ?? targetX,
+    targetY: targetEndpoint?.y ?? targetY,
+    targetPosition: targetEndpoint?.position ?? targetPosition,
     curvature: 0.28,
   });
 
@@ -55,6 +153,7 @@ export function ConditionEdge({
       <BaseEdge
         id={id}
         path={path}
+        markerEnd={markerEnd}
         style={{
           stroke: selected ? "var(--primary)" : "var(--muted-soft)",
           strokeWidth: selected ? 2.5 : 1.5,

frontend/src/components/workflow/WorkflowCanvas.tsx

@@ -7,6 +7,7 @@ import {
   type Connection,
   Controls,
   type Edge,
+  MarkerType,
   type Node,
   type NodeChange,
   type OnConnectEnd,
@@ -588,7 +589,16 @@ export function WorkflowCanvas({
                 }}
                 fitView
                 proOptions={{ hideAttribution: true }}
-                defaultEdgeOptions={{ type: "condition", animated: true }}
+                defaultEdgeOptions={{
+                  type: "condition",
+                  animated: true,
+                  markerEnd: {
+                    type: MarkerType.ArrowClosed,
+                    color: "var(--muted-soft)",
+                    width: 18,
+                    height: 18,
+                  },
+                }}
               >
                 <Background
                   variant={BackgroundVariant.Dots}