test: fix flaky no_workflow.webp screenshot test (#9458)

## Summary

Fix flaky `no_workflow.webp` screenshot test by waiting for async upload
and `/view` response before asserting.

## Changes

- **What**: In `loadWorkflowInMedia.spec.ts`, added `waitForUpload:
true` for `no_workflow.webp` and a `waitForResponse` call for the
`/view` endpoint. This ensures the error toast (from the 500 response)
is consistently visible before the screenshot assertion.

## Review Focus

The fix is scoped to `no_workflow.webp` only (via a `filesWithUpload`
Set) since it's the only test file that triggers an upload + `/view`
call. Other media files embed workflows and don't hit this path.

Fixes #9450

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-9458-test-fix-flaky-no_workflow-webp-screenshot-test-31b6d73d365081b88deaee91769baec1)
by [Unito](https://www.unito.io)

---------

Co-authored-by: GitHub Action <action@github.com>
Co-authored-by: Alexander Brown <drjkl@comfy.org>

browser_tests/tests/loadWorkflowInMedia.spec.ts

@@ -29,11 +29,23 @@ test.describe(
       // Currently opens missing nodes dialog which is outside scope of AVIF loading functionality
       // 'workflow.avif'
     ]
+    const filesWithUpload = new Set(['no_workflow.webp'])
+
     fileNames.forEach(async (fileName) => {
       test(`Load workflow in ${fileName} (drop from filesystem)`, async ({
         comfyPage
       }) => {
-        await comfyPage.dragDrop.dragAndDropFile(`workflowInMedia/${fileName}`)
+        const waitForUpload = filesWithUpload.has(fileName)
+        await comfyPage.dragDrop.dragAndDropFile(
+          `workflowInMedia/${fileName}`,
+          { waitForUpload }
+        )
+        if (waitForUpload) {
+          await comfyPage.page.waitForResponse(
+            (resp) => resp.url().includes('/view') && resp.status() !== 0,
+            { timeout: 10000 }
+          )
+        }
         await expect(comfyPage.canvas).toHaveScreenshot(`${fileName}.png`)
       })
     })