Fix vue node slot position calculation (#7877)

## Summary

Fix slot position for Vue nodes using LiteGraph calculation

Fixes #7446

## Changes
- Updated getInput/OutputPos to call getSlotPosition which handles
positions for both LiteGraph & Vue nodes correctly
- Add regression test

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-7877-Fix-vue-node-slot-position-calculation-2e16d73d365081219afef0e4ebfb0620)
by [Unito](https://www.unito.io)

---------

Co-authored-by: github-actions <github-actions@github.com>

browser_tests/tests/vueNodes/interactions/links/linkInteraction.spec.ts

@@ -102,7 +102,7 @@ test.describe('Vue Node Link Interaction', () => {
   test.beforeEach(async ({ comfyPage }) => {
     await comfyPage.setSetting('Comfy.UseNewMenu', 'Top')
     await comfyPage.setSetting('Comfy.VueNodes.Enabled', true)
-    await comfyPage.setup()
+    // await comfyPage.setup()
     await comfyPage.loadWorkflow('vueNodes/simple-triple')
     await comfyPage.vueNodes.waitForNodes()
     await fitToViewInstant(comfyPage)
@@ -993,4 +993,51 @@ test.describe('Vue Node Link Interaction', () => {
       expect(linked).toBe(true)
     })
   })
+
+  test('Dragging from subgraph input connects to correct slot', async ({
+    comfyPage,
+    comfyMouse
+  }) => {
+    // Setup workflow with a KSampler node
+    await comfyPage.executeCommand('Comfy.NewBlankWorkflow')
+    await comfyPage.waitForGraphNodes(0)
+    await comfyPage.executeCommand('Workspace.SearchBox.Toggle')
+    await comfyPage.nextFrame()
+    await comfyPage.searchBox.fillAndSelectFirstNode('KSampler')
+    await comfyPage.waitForGraphNodes(1)
+
+    // Convert the KSampler node to a subgraph
+    let ksamplerNode = (await comfyPage.getNodeRefsByType('KSampler'))?.[0]
+    await comfyPage.vueNodes.selectNode(String(ksamplerNode.id))
+    await comfyPage.executeCommand('Comfy.Graph.ConvertToSubgraph')
+
+    // Enter the subgraph
+    await comfyPage.vueNodes.enterSubgraph()
+    await fitToViewInstant(comfyPage)
+
+    // Get the KSampler node inside the subgraph
+    ksamplerNode = (await comfyPage.getNodeRefsByType('KSampler', true))?.[0]
+    const positiveInput = await ksamplerNode.getInput(1)
+    const negativeInput = await ksamplerNode.getInput(2)
+
+    const positiveInputPos = await getSlotCenter(
+      comfyPage.page,
+      ksamplerNode.id,
+      1,
+      true
+    )
+
+    const sourceSlot = await comfyPage.getSubgraphInputSlot()
+    const calculatedSourcePos = await sourceSlot.getOpenSlotPosition()
+
+    await comfyMouse.move(calculatedSourcePos)
+    await comfyMouse.drag(positiveInputPos)
+    await comfyMouse.drop()
+
+    // Verify connection went to the correct slot
+    const positiveLinks = await positiveInput.getLinkCount()
+    const negativeLinks = await negativeInput.getLinkCount()
+    expect(positiveLinks).toBe(1)
+    expect(negativeLinks).toBe(0)
+  })
 })