Add UI code for configuring subgraphNode widgets (#5826)

The third PR for managing display of widgets on subgraph nodes. This is
the one that actually makes the functionality usable and user visible.

Adds
- A right-side modal for configuring which widgets are promoted,
accessed by right click or selection toolbar
- This menu allows for re-arranging widget order by dragging and
dropping.
- Indicators inside the subgraph for which widgets have been promoted.
- Context menu options for promoting or demoting widget inside of a
subgraph.
<img width="767" height="694" alt="image"
src="https://github.com/user-attachments/assets/4f78645d-7b26-48ba-8c49-78f4807e89e8"
/>
<img width="784" height="435" alt="image"
src="https://github.com/user-attachments/assets/7005c730-a732-481e-befb-57019a8a31a7"
/>


Known issues
- Some preview widgets are not added to a node until a draw operation
occurs. The code does not yet have a way of determining which nodes
should have draw operations forced to facilitate initial widget
creation.

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-5826-Add-UI-code-for-configuring-subgraphNode-widgets-27c6d73d36508146accbf395e5bcd36a)
by [Unito](https://www.unito.io)

src/lib/litegraph/src/LGraphNode.ts

@@ -3749,6 +3749,13 @@ export class LGraphNode
     return !isHidden
   }
 
+  updateComputedDisabled() {
+    if (!this.widgets) return
+    for (const widget of this.widgets)
+      widget.computedDisabled =
+        widget.disabled || this.getSlotFromWidget(widget)?.link != null
+  }
+
   drawWidgets(
     ctx: CanvasRenderingContext2D,
     { lowQuality = false, editorAlpha = 1 }: DrawWidgetsOptions
@@ -3762,6 +3769,7 @@ export class LGraphNode
     ctx.save()
     ctx.globalAlpha = editorAlpha
 
+    this.updateComputedDisabled()
     for (const widget of widgets) {
       if (!this.isWidgetVisible(widget)) continue
 
@@ -3771,9 +3779,6 @@ export class LGraphNode
         : LiteGraph.WIDGET_OUTLINE_COLOR
 
       widget.last_y = y
-      // Disable widget if it is disabled or if the value is passed from socket connection.
-      widget.computedDisabled =
-        widget.disabled || this.getSlotFromWidget(widget)?.link != null
 
       ctx.strokeStyle = outlineColour
       ctx.fillStyle = '#222'