hotfix: stabilize flaky workflow sidebar browser tests (#7280)

## Summary
- Fix flaky workflow sidebar browser tests that were failing in headless
mode
- Add retry logic for menu hover operations in Topbar
- Add proper timing/wait helpers for dialog masks and workflow service
completion
- Fix test isolation issues in setupWorkflowsDirectory and drop workflow
test

## Test plan
- [x] Run `pnpm test:browser --
browser_tests/tests/sidebar/workflows.spec.ts` multiple times
- [x] Verify the 3 previously failing tests now pass consistently:
  - "Can overwrite other workflows with save as"
  - "Can rename nested workflow from opened workflow item"  
  - "Can drop workflow from workflows sidebar"

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-7280-hotfix-stabilize-flaky-workflow-sidebar-browser-tests-2c46d73d365081c5b3badfafe35a63dc)
by [Unito](https://www.unito.io)

---------

Co-authored-by: Terry Jia <terryjia88@gmail.com>
Co-authored-by: Alexander Brown <drjkl@comfy.org>
Co-authored-by: Luke Mino-Altherr <luke@comfy.org>
Co-authored-by: Claude <noreply@anthropic.com>
Co-authored-by: GitHub Action <action@github.com>
Co-authored-by: Benjamin Lu <benjaminlu1107@gmail.com>

browser_tests/tests/sidebar/workflows.spec.ts

@@ -340,6 +340,11 @@ test.describe('Workflows sidebar', () => {
 
     await comfyPage.menu.workflowsTab.open()
 
+    // Wait for workflow to appear in Browse section after sync
+    const workflowItem =
+      comfyPage.menu.workflowsTab.getPersistedItem('workflow1.json')
+    await expect(workflowItem).toBeVisible({ timeout: 3000 })
+
     const nodeCount = await comfyPage.getGraphNodesCount()
 
     // Get the bounding box of the canvas element
@@ -358,6 +363,10 @@ test.describe('Workflows sidebar', () => {
       '#graph-canvas',
       { targetPosition }
     )
-    expect(await comfyPage.getGraphNodesCount()).toBe(nodeCount * 2)
+
+    // Wait for nodes to be inserted after drag-drop with retryable assertion
+    await expect
+      .poll(() => comfyPage.getGraphNodesCount(), { timeout: 3000 })
+      .toBe(nodeCount * 2)
   })
 })