fix: simplify ensureCorrectLayoutScale and fix link sync during Vue node drag (#9680)

## Summary

Fix node layout drift from repeated `ensureCorrectLayoutScale` scaling,
simplify it to a pure one-time normalizer, and fix links not following
Vue nodes during drag.

## Changes

- **What**:
- `ensureCorrectLayoutScale` simplified to a one-time normalizer:
unprojects legacy Vue-scaled coordinates back to canonical LiteGraph
coordinates, marks the graph as corrected, and does nothing else. No
longer touches the layout store, syncs reroutes, or changes canvas
scale.
- Removed no-op calls from `useVueNodeLifecycle.ts` (a renderer version
string was passed where an `LGraph` was expected).
- `layoutStore.finalizeOperation` now calls `notifyChange` synchronously
instead of via `setTimeout`. This ensures `useLayoutSync`'s `onChange`
callback pushes positions to LiteGraph `node.pos` and calls
`canvas.setDirty()` within the same RAF frame as a drag update, fixing
links not following Vue nodes during drag.
- **Tests**: Added tests for `ensureCorrectLayoutScale` (idempotency,
round-trip, unknown-renderer no-op) and `graphRenderTransform`
(project/unproject round-trips, anchor caching).

## Review Focus

- The `setTimeout(() => this.notifyChange(change), 0)` →
`this.notifyChange(change)` change in `layoutStore.ts` is the key fix
for the drag-link-sync bug. The listener (`useLayoutSync`) only writes
to LiteGraph, not back to the layout store, so synchronous notification
is safe.
- `ensureCorrectLayoutScale` no longer has any side effects beyond
normalizing coordinates and setting `workflowRendererVersion` metadata.

---------

Co-authored-by: Amp <amp@ampcode.com>
Co-authored-by: Christian Byrne <cbyrne@comfy.org>
Co-authored-by: jaeone94 <89377375+jaeone94@users.noreply.github.com>
Co-authored-by: AustinMroz <austin@comfy.org>
Co-authored-by: Hunter <huntcsg@users.noreply.github.com>
Co-authored-by: GitHub Action <action@github.com>

browser_tests/tests/rendererToggleStability.spec.ts

@@ -0,0 +1,104 @@
+import {
+  comfyExpect as expect,
+  comfyPageFixture as test
+} from '../fixtures/ComfyPage'
+import type { ComfyPage } from '../fixtures/ComfyPage'
+import type { Position } from '../fixtures/types'
+
+type NodeSnapshot = { id: number } & Position
+
+async function getAllNodePositions(
+  comfyPage: ComfyPage
+): Promise<NodeSnapshot[]> {
+  return comfyPage.page.evaluate(() =>
+    window.app!.graph.nodes.map((n) => ({
+      id: n.id as number,
+      x: n.pos[0],
+      y: n.pos[1]
+    }))
+  )
+}
+
+async function getNodePosition(
+  comfyPage: ComfyPage,
+  nodeId: number
+): Promise<Position | undefined> {
+  return comfyPage.page.evaluate((targetNodeId) => {
+    const node = window.app!.graph.nodes.find((n) => n.id === targetNodeId)
+    if (!node) return
+
+    return {
+      x: node.pos[0],
+      y: node.pos[1]
+    }
+  }, nodeId)
+}
+
+async function expectNodePositionStable(
+  comfyPage: ComfyPage,
+  initial: NodeSnapshot,
+  mode: string
+) {
+  await expect
+    .poll(
+      async () => {
+        const current = await getNodePosition(comfyPage, initial.id)
+        return current?.x ?? Number.NaN
+      },
+      { message: `node ${initial.id} x drifted in ${mode} mode` }
+    )
+    .toBeCloseTo(initial.x, 1)
+
+  await expect
+    .poll(
+      async () => {
+        const current = await getNodePosition(comfyPage, initial.id)
+        return current?.y ?? Number.NaN
+      },
+      { message: `node ${initial.id} y drifted in ${mode} mode` }
+    )
+    .toBeCloseTo(initial.y, 1)
+}
+
+async function setVueMode(comfyPage: ComfyPage, enabled: boolean) {
+  await comfyPage.settings.setSetting('Comfy.VueNodes.Enabled', enabled)
+  if (enabled) {
+    await comfyPage.vueNodes.waitForNodes()
+  }
+  await comfyPage.nextFrame()
+}
+
+test.describe(
+  'Renderer toggle stability',
+  { tag: ['@node', '@canvas'] },
+  () => {
+    test('node positions do not drift when toggling between Vue and LiteGraph renderers', async ({
+      comfyPage
+    }) => {
+      const TOGGLE_COUNT = 5
+
+      const initialPositions = await getAllNodePositions(comfyPage)
+      expect(initialPositions.length).toBeGreaterThan(0)
+
+      for (let i = 0; i < TOGGLE_COUNT; i++) {
+        await setVueMode(comfyPage, true)
+        for (const initial of initialPositions) {
+          await expectNodePositionStable(
+            comfyPage,
+            initial,
+            `Vue toggle ${i + 1}`
+          )
+        }
+
+        await setVueMode(comfyPage, false)
+        for (const initial of initialPositions) {
+          await expectNodePositionStable(
+            comfyPage,
+            initial,
+            `LiteGraph toggle ${i + 1}`
+          )
+        }
+      }
+    })
+  }
+)