fix: Use strokeOpacity and stroke color for SVG hit detection

The invisible path needs an actual stroke color (just made invisible via
strokeOpacity=0) for SVG to register pointer events on the stroke area.
Also added react-flow__edge-interaction class for consistency with the
legacy builder pattern.

autogpt_platform/frontend/src/app/(platform)/build/components/FlowEditor/edges/CustomEdge.tsx

@@ -67,9 +67,10 @@ const CustomEdge = ({
       <path
         d={edgePath}
         fill="none"
-        stroke="transparent"
+        stroke="black"
+        strokeOpacity={0}
         strokeWidth={20}
-        className="cursor-pointer"
+        className="react-flow__edge-interaction cursor-pointer"
         onMouseEnter={() => setIsHovered(true)}
         onMouseLeave={() => setIsHovered(false)}
       />