test(infra): AssetHelper with builder pattern + deterministic fixtures (#10545)

## What

Adds `AssetHelper` — a builder-pattern helper for mocking asset-related
API endpoints in Playwright E2E tests, plus deterministic fixture data.

## Why

12+ asset-related API endpoints need mocking for asset browser tests
(PNL-02), cloud dialog testing (DLG-08), and other asset-dependent E2E
scenarios. Random mock data from existing `createMockAssets()` is
unsuitable for deterministic E2E assertions.

## What's included

### `AssetHelper.ts` (307 LOC)
- Fluent builder API: `assetHelper.withModels(3).withImages(5).mock()`
- Stateful mock store (Map) for upload→verify→delete flows
- Endpoint coverage: GET/POST/PUT/DELETE `/assets`, download progress
- `mockError()` for error state testing
- `clearMocks()` cleanup matching QueueHelper/FeatureFlagHelper pattern

### `assetFixtures.ts` (304 LOC)
- 11 stable named constants (checkpoints, loras, VAE, embedding, inputs,
outputs)
- Factory functions: `generateModels()`, `generateInputFiles()`,
`generateOutputAssets()`
- Fixed IDs/dates/sizes — no randomness, safe for screenshot comparisons

### ComfyPage integration
- Available as `comfyPage.assets` in all tests

## Testing
- TypeScript compiles clean
- Follows existing QueueHelper/FeatureFlagHelper conventions

## Unblocks
- PNL-02: Asset browser tests (@Jaewon Yoon)
- DLG-08: Assets modal / cloud dialog testing

Part of: Test Coverage Q2 Overhaul

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-10545-test-infra-AssetHelper-with-builder-pattern-deterministic-fixtures-32f6d73d365081d3985ef079ff3dbede)
by [Unito](https://www.unito.io)

---------

Co-authored-by: GitHub Action <action@github.com>

package.json

@@ -58,7 +58,6 @@
     "@atlaskit/pragmatic-drag-and-drop": "^1.3.1",
     "@comfyorg/comfyui-electron-types": "catalog:",
     "@comfyorg/design-system": "workspace:*",
-    "@comfyorg/ingest-types": "workspace:*",
     "@comfyorg/registry-types": "workspace:*",
     "@comfyorg/shared-frontend-utils": "workspace:*",
     "@comfyorg/tailwind-utils": "workspace:*",
@@ -123,6 +122,7 @@
     "zod-validation-error": "catalog:"
   },
   "devDependencies": {
+    "@comfyorg/ingest-types": "workspace:*",
     "@eslint/js": "catalog:",
     "@intlify/eslint-plugin-vue-i18n": "catalog:",
     "@lobehub/i18n-cli": "catalog:",