test(dashboard): migrate standalone mode Cypress spec to RTL

[sadpandajoe]

SUMMARY

Migrates the dashboard standalone-mode scenario from the deleted Cypress spec cypress-base/cypress/e2e/dashboard/_skip.load.test.ts (removed in #40384) to a component-level RTL test in DashboardBuilder.test.tsx. Part of the Cypress→Playwright/RTL migration epic.

The original Cypress spec opened ?edit=true&standalone=true and asserted three things. Two are already covered by existing unit tests; the new RTL test covers the third:

Original assertion	Where covered
?edit=true → discard-changes-button visible	URL→state in extractUrlParams.test.ts; state→DOM in Header.test.tsx (should render the "Discard changes" button under editMode: true).
?standalone=true → #app-menu not in DOM	#app-menu lives in Flask's spa.html and is gated server-side by {% if standalone_mode %} — out of RTL's reach. The React-side equivalent is ?standalone=2 (DashboardStandaloneMode.HideNavAndTitle), which makes DashboardBuilder suppress <DashboardHeader />. Net-new RTL test added.
Log emission (originally skipped as flaky)	Already covered by logger.test.ts (should POST an event to /superset/log/ when called).

The literal ?standalone=true parses to 1 (HideNav), which only hides the Flask-rendered app menu. Using standalone=2 documents the closest React-level contract and is called out in the test's comment.

BEFORE/AFTER SCREENSHOTS OR ANIMATED GIF

N/A — test-only change.

TESTING INSTRUCTIONS

```bash
cd superset-frontend
npm run test -- src/dashboard/components/DashboardBuilder/DashboardBuilder.test.tsx
```
All 25 tests should pass, including the new one:

• `should hide DashboardHeader when standalone mode hides nav and title (?standalone=2)`

ADDITIONAL INFORMATION

• Has associated issue:
• Required feature flags:
• Changes UI
• Includes DB Migration (follow approval process in SIP-59)
  • Migration is atomic, supports rollback & is backwards-compatible
  • Confirm DB migration upgrade and downgrade tested
  • Runtime estimates and downtime expectations provided
• Introduces new feature or API
• Removes existing feature or API

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 64.14%. Comparing base (8eda626) to head (8230b7e).
⚠️ Report is 47 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master   #40914   +/-   ##
=======================================
  Coverage   64.14%   64.14%           
=======================================
  Files        2653     2653           
  Lines      143525   143525           
  Branches    33120    33120           
=======================================
  Hits        92063    92063           
  Misses      49851    49851           
  Partials     1611     1611           

Flag	Coverage Δ
javascript	67.86% <ø> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

☔ View full report in Codecov by Harness.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.

[netlify]

✅ Deploy Preview for superset-docs-preview ready!

Name	Link
🔨 Latest commit	e6d770d
🔍 Latest deploy log	https://app.netlify.com/projects/superset-docs-preview/deploys/6a28640d5028980008fc38f6
😎 Deploy Preview	https://deploy-preview-40914--superset-docs-preview.netlify.app
📱 Preview on mobile	Toggle QR Code... Use your smartphone camera to open QR code link.
🤖 Make changes	Run an agent on this branch

---

To edit notification comments on pull requests, go to your Netlify project configuration.

[Copilot]

Pull request overview

Migrates the dashboard standalone-mode assertion from a removed Cypress _skip E2E spec into a React Testing Library component test, ensuring the React-side “standalone hides header” contract remains covered as part of the Cypress → RTL/Playwright migration effort.

Changes:

• Add an RTL test verifying ?standalone=2 (HideNavAndTitle) suppresses the DashboardHeader in DashboardBuilder.

[bito-code-review]

The suggestion to capture and restore the full window.location.href is appropriate. This approach ensures that the pathname and hash are preserved, preventing potential state leakage to subsequent tests. Below is the recommended update for the test setup:

const originalHref = window.location.href;
// ... test logic ...
window.history.replaceState({}, '', originalHref);

superset-frontend/src/dashboard/components/DashboardBuilder/DashboardBuilder.test.tsx

const originalHref = window.location.href;
// ... test logic ...
window.history.replaceState({}, '', originalHref);