The target → graph rename shipped in PR #17 but omnigraph.example.yaml
still used the old form (`targets:` / `cli.target`). Since the serde
struct uses `rename = "graphs"` without a `targets` alias, the example
wouldn't deserialize against current code.
Update the example to the new form. No alias is being added — the
deserialization error for old configs is loud and clear, which is the
better migration signal for a young project.