fix: LGraphGroup paste position (#9962)

## Summary

Fix group paste position: groups now paste at the cursor location
instead of on top of the original.

## Changes

- **What**: Added LGraphGroup offset handling in _deserializeItems()
position adjustment loop, matching existing LGraphNode and Reroute
behavior.

## Screenshots

Before:


https://github.com/user-attachments/assets/e317af10-8009-4092-9d14-de79316cd853

After:


https://github.com/user-attachments/assets/f4ffefd5-519a-4592-812c-c88e3b5940fd

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-9962-fix-LGraphGroup-paste-position-3246d73d365081eea5b2e2507da861de)
by [Unito](https://www.unito.io)

browser_tests/tests/groupCopyPaste.spec.ts

@@ -0,0 +1,44 @@
+import { expect } from '@playwright/test'
+
+import { comfyPageFixture as test } from '../fixtures/ComfyPage'
+
+test.describe('Group Copy Paste', { tag: ['@canvas'] }, () => {
+  test.afterEach(async ({ comfyPage }) => {
+    await comfyPage.canvasOps.resetView()
+  })
+
+  test('Pasted group is offset from original position', async ({
+    comfyPage
+  }) => {
+    await comfyPage.workflow.loadWorkflow('groups/single_group_only')
+
+    const titlePos = await comfyPage.page.evaluate(() => {
+      const app = window.app!
+      const group = app.graph.groups[0]
+      const clientPos = app.canvasPosToClientPos([
+        group.pos[0] + 50,
+        group.pos[1] + 15
+      ])
+      return { x: clientPos[0], y: clientPos[1] }
+    })
+    await comfyPage.canvas.click({ position: titlePos })
+    await comfyPage.nextFrame()
+
+    await comfyPage.clipboard.copy()
+    await comfyPage.clipboard.paste()
+    await comfyPage.nextFrame()
+
+    const positions = await comfyPage.page.evaluate(() =>
+      window.app!.graph.groups.map((g: { pos: number[] }) => ({
+        x: g.pos[0],
+        y: g.pos[1]
+      }))
+    )
+
+    expect(positions).toHaveLength(2)
+    const dx = Math.abs(positions[0].x - positions[1].x)
+    const dy = Math.abs(positions[0].y - positions[1].y)
+    expect(dx).toBeCloseTo(50, 0)
+    expect(dy).toBeCloseTo(15, 0)
+  })
+})