Node ghost mode when adding nodes (#8694)

## Summary

Adds option for adding a node as a "ghost" that follows the cursor until
the user left clicks to confirm, or esc/right click to cancel.

## Changes

- **What**: 
Adds option for `ghost` when calling `graph.add`  
This adds the node with a `flag` of ghost which causes it to render
transparent
Selects the node, then sets the canvas as dragging to stick the node to
the cursor

## Screenshots (if applicable)



https://github.com/user-attachments/assets/dcb5702f-aba3-4983-aa40-c51f24a4767a

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-8694-Node-ghost-mode-when-adding-nodes-2ff6d73d3650815591f2c28415050463)
by [Unito](https://www.unito.io)

src/renderer/extensions/vueNodes/components/LGraphNode.vue

@@ -29,7 +29,7 @@
           'ring-4 ring-primary-500 bg-primary-500/10': isDraggingOver
         },
 
-        shouldHandleNodePointerEvents
+        shouldHandleNodePointerEvents && !nodeData.flags?.ghost
           ? 'pointer-events-auto'
           : 'pointer-events-none',
         !isCollapsed && ' pb-1'
@@ -268,6 +268,8 @@ const muted = computed((): boolean => nodeData.mode === LGraphEventMode.NEVER)
 const nodeOpacity = computed(() => {
   const globalOpacity = settingStore.get('Comfy.Node.Opacity') ?? 1
 
+  if (nodeData.flags?.ghost) return globalOpacity * 0.3
+
   // For muted/bypassed nodes, apply the 0.5 multiplier on top of global opacity
   if (bypassed.value || muted.value) {
     return globalOpacity * 0.5