Cleanup: Litegraph/Vue synchronization work (#5789)

## Summary

Cleanup and fixes to the existing syncing logic.

## Review Focus

This is probably enough to review and test now.

Main things that should still work: 
- moving nodes around
- adding new ones
- switching back and forth between Vue and Litegraph

Let me know if you find any bugs that weren't already present there.

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-5789-WIP-Litegraph-Vue-synchronization-work-27a6d73d3650811682cacacb82367b9e)
by [Unito](https://www.unito.io)

src/lib/litegraph/src/LGraphCanvas.ts

@@ -757,9 +757,7 @@ export class LGraphCanvas
 
     // Initialize link renderer if graph is available
     if (graph) {
-      this.linkRenderer = new LitegraphLinkAdapter(graph)
-      // Disable layout writes during render
-      this.linkRenderer.enableLayoutStoreWrites = false
+      this.linkRenderer = new LitegraphLinkAdapter(false)
     }
 
     this.linkConnector.events.addEventListener('link-created', () =>
@@ -1858,9 +1856,7 @@ export class LGraphCanvas
     newGraph.attachCanvas(this)
 
     // Re-initialize link renderer with new graph
-    this.linkRenderer = new LitegraphLinkAdapter(newGraph)
-    // Disable layout writes during render
-    this.linkRenderer.enableLayoutStoreWrites = false
+    this.linkRenderer = new LitegraphLinkAdapter(false)
 
     this.dispatch('litegraph:set-graph', { newGraph, oldGraph: graph })
     this.#dirty()

src/lib/litegraph/src/types/widgets.ts

@@ -251,6 +251,8 @@ export interface IBaseWidget<
   TType extends string = string,
   TOptions extends IWidgetOptions<unknown> = IWidgetOptions<unknown>
 > {
+  [symbol: symbol]: boolean
+
   linkedWidgets?: IBaseWidget[]
 
   name: string