test: #3633139 Add functional tests for Varbase AI SEO

Issue: https://www.drupal.org/i/3633139

Adds the Varbase functional testing suite (@vardot/varbase-e2e) and a varbase-e2e-test job: a fresh Varbase 11 site, the recipe applied twice, 7 scenarios, no AI key.

• CI uses the AI module test provider (EchoAI).
• Replaces the old smoke tests, custom steps and browser-made users.

Scenarios (7):

01-01-ai-seo-setup.feature

• Check the SEO title and description automators for blog posts and utility pages
• Check the ECA model that writes the meta tags on save is enabled

01-02-ai-seo-on-save.feature

• Verify empty SEO fields of a blog post are written on save
• Verify an SEO title the editor wrote is kept
• Verify a blog post with no content gets no SEO text invented

01-03-ai-seo-bulk.feature

• Check the "SEO admin" user gets the AI SEO meta tags page and its actions
• Check the "Site admin" user gets the AI SEO meta tags page and its actions

Green locally with gitlab-ci-local: 7 passed.

AI-Generated: Yes

Checkpoints:

• File an issue
• Addition/Change/Update/Fix
• Testing to ensure no regression
• Automated unit testing coverage
• Automated functional testing coverage
• UX/UI designer responsibilities
• Readability
• Accessibility
• Performance
• Security
• Developer Documentation
• User Guide Documentation
• Reviewed by human
• Code review by maintainers
• Full testing and approval
• Credit contributors
• Review with the product owner
• Release notes snippet
• Release

🤖 Generated with Claude Code