🐛 Describe the bug

A single-node pipeline is a valid DAG, but KDP doesn't support it. This is because spec.graph.edges is required by the CRD schema.

📜 To Reproduce

Steps to reproduce the behavior:

1. Create a pipeline with only 1 node and no entry for spec.graph.edges
2. Apply it to the cluster
3. It will get rejected due to failed schema validation