feat(cloud): add asset widget support for PrimitiveNode model selection (#8598)

Add cloud asset widget creation in `_createWidget()` using
`isAssetBrowserEligible()`
- Extract shared `createAssetWidget` factory to
`src/platform/assets/utils/`
- Refactor `useComboWidget.ts` to use the shared factory
- Add `_finalizeWidget()` helper to DRY up widget sizing/callback setup
- Pass target node's `comfyClass` and input name to Asset Browser for
correct model filtering
- Check `Comfy.Assets.UseAssetAPI` setting (matches `useComboWidget.ts`
behavior)
- Sync existing target widget value to asset widget
- Add toast notifications for asset validation errors
- Add i18n translations for invalidAsset and invalidFilename errors

Supersedes #8461 (clean rebase, no merge commits)

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-8598-feat-cloud-add-asset-widget-support-for-PrimitiveNode-model-selection-2fd6d73d365081a8afa7c2e91762f11c)
by [Unito](https://www.unito.io)


<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->

## Summary by CodeRabbit

* **New Features**
* Introduced asset widget integration for cloud-based model selection,
enabling users to browse and select assets through an improved
interface.
* Added comprehensive asset validation with enhanced error messages for
invalid assets and filenames.

<!-- end of auto-generated comment: release notes by coderabbit.ai -->

---------

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src/platform/assets/utils/createAssetWidget.ts

@@ -0,0 +1,111 @@
+import { t } from '@/i18n'
+import type { LGraphNode } from '@/lib/litegraph/src/litegraph'
+import type {
+  IBaseWidget,
+  IWidgetAssetOptions
+} from '@/lib/litegraph/src/types/widgets'
+import { useAssetBrowserDialog } from '@/platform/assets/composables/useAssetBrowserDialog'
+import {
+  assetFilenameSchema,
+  assetItemSchema
+} from '@/platform/assets/schemas/assetSchema'
+import { useToastStore } from '@/platform/updates/common/toastStore'
+import { getAssetFilename } from '@/platform/assets/utils/assetMetadataUtils'
+
+interface CreateAssetWidgetParams {
+  /** The node to add the widget to */
+  node: LGraphNode
+  /** The widget name */
+  widgetName: string
+  /** The node type to show in asset browser (may differ from node.comfyClass for PrimitiveNode) */
+  nodeTypeForBrowser: string
+  /** Input name for asset browser filtering (defaults to widgetName if not provided) */
+  inputNameForBrowser?: string
+  /** Default value for the widget */
+  defaultValue?: string
+  /** Callback when widget value changes */
+  onValueChange?: (
+    widget: IBaseWidget,
+    newValue: string,
+    oldValue: unknown
+  ) => void
+}
+
+/**
+ * Creates an asset widget that opens the Asset Browser dialog for model selection.
+ * Used by both regular nodes (via useComboWidget) and PrimitiveNode.
+ *
+ * @param params - Configuration for the asset widget
+ * @returns The created asset widget
+ */
+export function createAssetWidget(
+  params: CreateAssetWidgetParams
+): IBaseWidget {
+  const {
+    node,
+    widgetName,
+    nodeTypeForBrowser,
+    inputNameForBrowser,
+    defaultValue,
+    onValueChange
+  } = params
+
+  const displayLabel = defaultValue ?? t('widgets.selectModel')
+  const assetBrowserDialog = useAssetBrowserDialog()
+
+  async function openModal(widget: IBaseWidget) {
+    const toastStore = useToastStore()
+
+    await assetBrowserDialog.show({
+      nodeType: nodeTypeForBrowser,
+      inputName: inputNameForBrowser ?? widgetName,
+      currentValue: widget.value as string,
+      onAssetSelected: (asset) => {
+        const validatedAsset = assetItemSchema.safeParse(asset)
+
+        if (!validatedAsset.success) {
+          console.error(
+            'Invalid asset item:',
+            validatedAsset.error.errors,
+            'Received:',
+            asset
+          )
+          toastStore.add({
+            severity: 'error',
+            summary: t('assetBrowser.invalidAsset'),
+            detail: t('assetBrowser.invalidAssetDetail'),
+            life: 5000
+          })
+          return
+        }
+
+        const filename = getAssetFilename(validatedAsset.data)
+        const validatedFilename = assetFilenameSchema.safeParse(filename)
+
+        if (!validatedFilename.success) {
+          console.error(
+            'Invalid asset filename:',
+            validatedFilename.error.errors,
+            'for asset:',
+            validatedAsset.data.id
+          )
+          toastStore.add({
+            severity: 'error',
+            summary: t('assetBrowser.invalidFilename'),
+            detail: t('assetBrowser.invalidFilenameDetail'),
+            life: 5000
+          })
+          return
+        }
+
+        const oldValue = widget.value
+        widget.value = validatedFilename.data
+        onValueChange?.(widget, validatedFilename.data, oldValue)
+      }
+    })
+  }
+
+  const options: IWidgetAssetOptions = { openModal }
+
+  return node.addWidget('asset', widgetName, displayLabel, () => {}, options)
+}