Use when the user wants to bring a Kustomize overlay or base into ConfigHub as Units — phrases like "I have a kustomization.yaml, how do I use it with ConfigHub?", "import my Kustomize overlays", "migrate from Kustomize to ConfigHub", "render this overlay into ConfigHub", "kustomize build into Units", or "I have a base + overlays directory structure". Runs `kustomize build` locally, splits the result into one or more ConfigHub Units via `cub unit create`, and hands off ongoing customization to `cub-mutate`. Do not load for Flux `Kustomization` CRDs (use `import-from-flux` — that's the renderer-bridge pipeline), for Helm charts (use `import-from-helm`), for adopting live cluster resources (use `import-from-cluster`), or for authoring raw YAML from scratch (use `config-as-data`).