Fix Node Highlight on Task Hover (#1401)

## Description

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Fixes a bug where dragging from the component library over a node on the canvas to replace it would not highlight the replace-target node.

## Related Issue and Pull requests

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Closes Shopify/oasis-frontend#326

## Type of Change

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- [x] Bug fix

## Checklist

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- [ ] I have tested this does not break current pipelines / runs functionality
- [ ] I have tested the changes on staging

## Screenshots (if applicable)

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## Test Instructions

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1. Drag a task from the library and hover over a node on the canvas, it should highlight orange.
2. It should un-highlight when you move off it
3. Replace flow should trigger if you release while it is highlighted

## Additional Comments



Future: disable highlighting when an IO node is dragged over a task

<!-- Add any additional context or information that reviewers might need to know regarding this PR -->

Author: camielvs

src/components/shared/ReactFlow/FlowCanvas/FlowCanvas.tsx

@@ -575,13 +575,19 @@ const FlowCanvas = ({
           isPositionInNode(node, cursorPosition),
         );
 
-        if (hoveredNode?.id === replaceTarget?.id) return;
-        if (hoveredNode?.type && !REPLACEABLE_NODES.has(hoveredNode.type)) {
+        if (!hoveredNode && replaceTarget) {
           setReplaceTarget(null);
           return;
         }
 
-        setReplaceTarget(hoveredNode || null);
+        if (!hoveredNode || hoveredNode.id === replaceTarget?.id) return;
+
+        if (hoveredNode.type && !REPLACEABLE_NODES.has(hoveredNode.type)) {
+          setReplaceTarget(null);
+          return;
+        }
+
+        setReplaceTarget(hoveredNode);
       }
     },
     [reactFlowInstance, nodes, replaceTarget, setReplaceTarget],
@@ -912,7 +918,12 @@ const FlowCanvas = ({
     preserveIOSelectionOnSpecChange(componentSpec);
     updateReactFlow(componentSpec);
     initialCanvasLoaded.current = true;
-  }, [componentSpec, currentSubgraphPath, preserveIOSelectionOnSpecChange]);
+  }, [
+    replaceTarget,
+    componentSpec,
+    currentSubgraphPath,
+    preserveIOSelectionOnSpecChange,
+  ]);
 
   useEffect(() => {
     reactFlowInstance?.fitView({