Defer vue node layout calculations on hidden browser tabs (#8805)

## Summary

If you load the window in Nodes 2.0, then switch tabs while it is still
loading, the position of the nodes is calculated incorrectly due to
useElementBounding returning left=0, top=0 for the canvas element in a
hidden tab, causing clientPosToCanvasPos to miscalculate node positions
from the ResizeObserver measurements

## Changes

- **What**: 
- Store observed elements while document is in hidden state
- Re-observe when tab becomes visible

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-8805-Defer-vue-node-layout-calculations-on-hidden-browser-tabs-3046d73d365081019ae6c403c0ac6d1a)
by [Unito](https://www.unito.io)

Author: pythongosssss

src/renderer/extensions/vueNodes/composables/useVueNodeResizeTracking.ts

@@ -8,9 +8,11 @@
  * Supports different element types (nodes, slots, widgets, etc.) with
  * customizable data attributes and update handlers.
  */
-import { getCurrentInstance, onMounted, onUnmounted, toValue } from 'vue'
+import { getCurrentInstance, onMounted, onUnmounted, toValue, watch } from 'vue'
 import type { MaybeRefOrGetter } from 'vue'
 
+import { useDocumentVisibility } from '@vueuse/core'
+
 import { useSharedCanvasPositionConversion } from '@/composables/element/useCanvasPositionConversion'
 import { LiteGraph } from '@/lib/litegraph/src/litegraph'
 import { layoutStore } from '@/renderer/core/layout/store/layoutStore'
@@ -59,9 +61,37 @@ const trackingConfigs: Map<string, ElementTrackingConfig> = new Map([
   ]
 ])
 
+// Elements whose ResizeObserver fired while the tab was hidden
+const deferredElements = new Set<HTMLElement>()
+const visibility = useDocumentVisibility()
+
+watch(visibility, (state) => {
+  if (state !== 'visible' || deferredElements.size === 0) return
+
+  // Re-observe deferred elements to trigger fresh measurements
+  for (const element of deferredElements) {
+    if (element.isConnected) {
+      resizeObserver.observe(element)
+    }
+  }
+  deferredElements.clear()
+})
+
 // Single ResizeObserver instance for all Vue elements
 const resizeObserver = new ResizeObserver((entries) => {
   if (useCanvasStore().linearMode) return
+
+  // Skip measurements when tab is hidden — bounding rects are unreliable
+  if (visibility.value === 'hidden') {
+    for (const entry of entries) {
+      if (entry.target instanceof HTMLElement) {
+        deferredElements.add(entry.target)
+        resizeObserver.unobserve(entry.target)
+      }
+    }
+    return
+  }
+
   // Canvas is ready when this code runs; no defensive guards needed.
   const conv = useSharedCanvasPositionConversion()
   // Group updates by type, then flush via each config's handler