feat: add ImageCompare node (#7538)

## Summary

add ImageCompare node, which is high demand among custom nodes, such as
rgthree, we should support as core node

Need BE change https://github.com/comfyanonymous/ComfyUI/pull/11343

## Screenshots (if applicable)



https://github.com/user-attachments/assets/a37bdcd0-de59-4bdd-bfc7-1adbe92f5298

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-7538-feat-add-ImageCompare-node-2cb6d73d36508163a7d5f4807aece01a)
by [Unito](https://www.unito.io)

src/extensions/core/imageCompare.ts

@@ -0,0 +1,48 @@
+import type { NodeExecutionOutput } from '@/schemas/apiSchema'
+import { api } from '@/scripts/api'
+import { app } from '@/scripts/app'
+import { useExtensionService } from '@/services/extensionService'
+
+useExtensionService().registerExtension({
+  name: 'Comfy.ImageCompare',
+
+  async nodeCreated(node) {
+    if (node.constructor.comfyClass !== 'ImageCompare') return
+
+    const [oldWidth, oldHeight] = node.size
+    node.setSize([Math.max(oldWidth, 400), Math.max(oldHeight, 350)])
+
+    const onExecuted = node.onExecuted
+
+    node.onExecuted = function (output: NodeExecutionOutput) {
+      onExecuted?.call(this, output)
+
+      const aImages = (output as Record<string, unknown>).a_images as
+        | Record<string, string>[]
+        | undefined
+      const bImages = (output as Record<string, unknown>).b_images as
+        | Record<string, string>[]
+        | undefined
+      const rand = app.getRandParam()
+
+      const beforeUrl =
+        aImages && aImages.length > 0
+          ? api.apiURL(`/view?${new URLSearchParams(aImages[0])}${rand}`)
+          : ''
+      const afterUrl =
+        bImages && bImages.length > 0
+          ? api.apiURL(`/view?${new URLSearchParams(bImages[0])}${rand}`)
+          : ''
+
+      const widget = node.widgets?.find((w) => w.type === 'imagecompare')
+
+      if (widget) {
+        widget.value = {
+          before: beforeUrl,
+          after: afterUrl
+        }
+        widget.callback?.(widget.value)
+      }
+    }
+  }
+})