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/scripts/ui/draggableList.ts

@@ -23,11 +23,8 @@
     OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
     SOFTWARE.
 */
-import { $el } from '../ui'
-
-$el('style', {
-  parent: document.head,
-  textContent: `
+const styleElement = document.createElement('style')
+styleElement.textContent = `
         .draggable-item {
             position: relative;
             will-change: transform;
@@ -40,7 +37,7 @@ $el('style', {
             z-index: 10;
         }
     `
-})
+document.head.append(styleElement)
 
 export class DraggableList extends EventTarget {
   listContainer