Krate CI Engine overview

Pipeline and Job scheduling engine backed by ARC (Actions Runner Controller). Defines RunnerPool CRDs with warm/max replica scaling, trust-tier admission, per-pool cache backends, and queue-depth KEDA autoscaling. Pipelines execute as Kubernetes Jobs with projected ServiceAccount tokens scoped to repo/ref/pipeline. Collects artifacts, streams logs via SSE, and supports rerun-from-step semantics.