Stack Context

This is Phase 7 of the BrowserStack Maestro E2E stack for Checkout Kit, stacked on GitHub E2E reporting.

Parent issue: https://github.com/shop/issues-checkout-kit/issues/1101
Epic: https://github.com/shop/issues-checkout-kit/issues/1084

What?

Adds the soft-launch controls and runbook for PR E2E checks:

• maps Bitrise pull requests to the e2e pipeline in e2e/bitrise.yml
• defaults BrowserStack Maestro execution to E2E_STRICT=false
• keeps assertion failures reportable without blocking initial PR progress
• adds BrowserStack API retry controls for 429/5xx responses
• attempts to stop BrowserStack builds on timeout
• documents retry, timeout, local rerun, and triage behavior in e2e/RUNBOOK.md
• documents soft-launch environment controls in Bitrise setup docs

Why?

The E2E pipeline should start non-blocking while the infrastructure and suite stabilize. Developers still get commit statuses, Check Runs, and actionable failure comments, but PR progress is not blocked until the team intentionally promotes checks to required.

Validation

shadowenv exec -- ruby e2e/test/soft_launch_test.rb
shadowenv exec -- ruby e2e/test/bitrise_pipeline_test.rb
shadowenv exec -- ruby e2e/test/github_reporter_test.rb
shadowenv exec -- ruby e2e/test/e2e_matrix_test.rb
shadowenv exec -- ruby e2e/test/browserstack_device_resolver_test.rb
shadowenv exec -- ruby e2e/test/maestro_suite_package_test.rb
shadowenv exec -- ruby -c e2e/scripts/browserstack_maestro
shadowenv exec -- ruby -c e2e/scripts/report_e2e_results
shadowenv exec -- bitrise validate -c e2e/bitrise.yml
shadowenv exec -- ruby -e 'require "yaml"; YAML.safe_load_file("e2e/bitrise.yml"); puts "e2e bitrise yaml parsed"'