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 -->

---------

Co-authored-by: Amp <amp@ampcode.com>
Co-authored-by: Subagent 5 <subagent@example.com>
Co-authored-by: GitHub Action <action@github.com>
Co-authored-by: guill <jacob.e.segal@gmail.com>
Co-authored-by: Jin Yi <jin12cc@gmail.com>
Co-authored-by: Alexander Brown <drjkl@comfy.org>
Co-authored-by: AustinMroz <austin@comfy.org>
Co-authored-by: Comfy Org PR Bot <snomiao+comfy-pr@gmail.com>
Co-authored-by: github-actions <github-actions@github.com>
Co-authored-by: Johnpaul Chiwetelu <49923152+Myestery@users.noreply.github.com>
Co-authored-by: Rizumu Ayaka <rizumu@ayaka.moe>
Co-authored-by: Kelly Yang <124ykl@gmail.com>
Co-authored-by: sno <snomiao@gmail.com>
Co-authored-by: Claude Sonnet 4.5 <noreply@anthropic.com>
Co-authored-by: Benjamin Lu <benjaminlu1107@gmail.com>
Co-authored-by: Terry Jia <terryjia88@gmail.com>
Co-authored-by: Luke Mino-Altherr <luke@comfy.org>
Co-authored-by: coderabbitai[bot] <136622811+coderabbitai[bot]@users.noreply.github.com>

src/lib/litegraph/src/litegraph.ts

@@ -150,7 +150,9 @@ export { BaseWidget } from './widgets/BaseWidget'
 
 export { LegacyWidget } from './widgets/LegacyWidget'
 
-export { isComboWidget, isAssetWidget } from './widgets/widgetMap'
+export { isComboWidget } from './widgets/widgetMap'
+/** @knipIgnoreUnusedButUsedByCustomNodes */
+export { isAssetWidget } from './widgets/widgetMap'
 // Additional test-specific exports
 export { LGraphButton } from './LGraphButton'
 export { MovingOutputLink } from './canvas/MovingOutputLink'

src/lib/litegraph/src/widgets/widgetMap.ts

@@ -141,7 +141,10 @@ export function isComboWidget(widget: IBaseWidget): widget is IComboWidget {
   return widget.type === 'combo'
 }
 
-/** Type guard: Narrow **from {@link IBaseWidget}** to {@link IAssetWidget}. */
+/**
+ * Type guard: Narrow **from {@link IBaseWidget}** to {@link IAssetWidget}.
+ * @knipIgnoreUnusedButUsedByCustomNodes
+ */
 export function isAssetWidget(widget: IBaseWidget): widget is IAssetWidget {
   return widget.type === 'asset'
 }