Tracking Issue

Nightly E2E scorecard with Slack notification — split into two deliverables:

• feat(ci): nightly E2E scorecard workflow with GitHub Actions summary #2613 — Scorecard workflow: scheduled GitHub Action that analyzes overnight runs and publishes metrics to the Actions job summary. No external dependencies.
• feat(ci): connect nightly scorecard to Slack channel #2614 — Slack integration: connect the scorecard to a Slack channel via incoming webhook. Requires admin setup (channel + webhook + repo secret).

See each issue for detailed design and acceptance criteria.