Complete AcademyLens readiness flow

[heznpc]

Summary

• add a browser-native Translator API availability probe without changing the default Google Translate runtime
• add sanitized logged-in courses fixtures plus DOM walker and E2E coverage for Gradual navigation/CTA boundaries
• add store screenshot capture workflow and tighten fixture/file hygiene checks

Verification

• npm test
• npm run check:files
• npm run test:e2e
• npm run store:screenshots
• npm run check:full