CI Observability overview

CI Observability as a cross-cutting topic - measuring and improving the health and performance of CI/CD systems themselves. Covers pipeline duration metrics and trend tracking, flaky-test detection and quarantine workflows, failure-rate dashboards, queue-time analysis for runner capacity planning, DORA metrics (deployment frequency, lead time, MTTR, change failure rate), and OpenTelemetry trace export from pipeline steps for distributed tracing of build workflows.