Scheduler-agnostic orchestration layer for the Culvert framework. Provides a cloud-neutral DAG model (DagSpec / TaskSpec) and a Pipeline -> DagSpec translator (T11.1). Renderers to Airflow / Cloud Composer (T11.3) and job-control wiring (T11.4) build on this model. Like data-pipeline-core, this module is cloud-neutral: it depends only on the contracts + java.util — no Beam, no Airflow, no GCP. Sprint-11 deliverable (epic #46, T11.1 / issue #61).