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/fixtures/components/SidebarTab.ts

@@ -137,6 +137,13 @@ export class WorkflowsSidebarTab extends SidebarTab {
       .click()
     await this.page.keyboard.type(newName)
     await this.page.keyboard.press('Enter')
+
+    // Wait for workflow service to finish renaming
+    await this.page.waitForFunction(
+      () => !window['app']?.extensionManager?.workflow?.isBusy,
+      undefined,
+      { timeout: 3000 }
+    )
   }
 
   async insertWorkflow(locator: Locator) {