feat: deduplicate subgraph node IDs on workflow load (experimental) (#8762)

## Summary

Add `ensureGlobalIdUniqueness` to reassign duplicate node IDs across
subgraphs when loading workflows, gated behind an experimental setting.

## Changes

- **What**: Shared `LGraphState` between root graph and subgraphs so ID
counters are global. Added `ensureGlobalIdUniqueness()` method that
detects and remaps colliding node IDs in subgraphs, preserving root
graph IDs as canonical and patching link references. Gated behind
`Comfy.Graph.DeduplicateSubgraphNodeIds` (experimental, default
`false`).
- **Dependencies**: None

## Review Focus

- Shared state override on `Subgraph` (getter delegates to root, setter
is no-op) — verify no existing code sets `subgraph.state` directly.
- `Math.max` state merging in `configure()` prevents ID counter
regression when loading subgraph definitions.
- Feature flag wiring: static property on `LGraph`, synced from settings
via `useLitegraphSettings`.

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-8762-feat-deduplicate-subgraph-node-IDs-on-workflow-load-experimental-3036d73d36508184b6cee5876dc4d935)
by [Unito](https://www.unito.io)

---------

Co-authored-by: Amp <amp@ampcode.com>
Co-authored-by: GitHub Action <action@github.com>

src/platform/settings/composables/useLitegraphSettings.ts

@@ -2,6 +2,7 @@ import { watchEffect } from 'vue'
 
 import {
   CanvasPointer,
+  LGraph,
   LGraphNode,
   LiteGraph
 } from '@/lib/litegraph/src/litegraph'
@@ -162,4 +163,10 @@ export const useLitegraphSettings = () => {
       'Comfy.EnableWorkflowViewRestore'
     )
   })
+
+  watchEffect(() => {
+    LGraph.deduplicateSubgraphIds = settingStore.get(
+      'Comfy.Graph.DeduplicateSubgraphNodeIds'
+    )
+  })
 }

src/platform/settings/constants/coreSettings.ts

@@ -1201,5 +1201,16 @@ export const CORE_SETTINGS: SettingParams[] = [
     defaultValue: false,
     experimental: true,
     versionAdded: '1.40.0'
+  },
+  {
+    id: 'Comfy.Graph.DeduplicateSubgraphNodeIds',
+    category: ['Comfy', 'Graph', 'Subgraph'],
+    name: 'Deduplicate subgraph node IDs',
+    tooltip:
+      'Automatically reassign duplicate node IDs in subgraphs when loading a workflow.',
+    type: 'boolean',
+    defaultValue: false,
+    experimental: true,
+    versionAdded: '1.40.0'
   }
 ]