Persist Cloud Native Buildpacks build caches across ephemeral CI runners with pack --cache-image, and understand the truly daemonless CI options (lifecycle/creator, Tekton, kpack).

Documented steps

1. Cache images preserve build-optimizing layers across host machines and are intended 'to improve performance when using pack in ephemeral environments such as CI/CD pipelines' (https://buildpacks.io/docs/for-app-developers/how-to/build-inputs/use-cache-image/).
2. `--cache-image <registry-image>` MUST be combined with `--publish` (documented on both the cache-image how-to and the pack build reference: 'Cache build layers in remote registry. Requires --publish').
3. Trust the builder first so it can access registry credentials when publishing: `pack config trusted-builders add <builder>`.
4. Example from the docs (local registry): `pack build localhost:5000/myapp --builder cnbs/sample-builder:resolute --path ./app --cache-image localhost:5000/myapp-cache:latest --network host --publish`. Omit --network host for a remote registry. A later build on a different runner reuses the same --cache-image value to restore cached layers.
5. Run `docker login` for the target registry before the build; clear a stale cache with `--clear-cache`, or configure cache explicitly with `--cache type=build;format=image;name=<image>` (format=image also requires --publish).
6. Registry cleanup is your responsibility: 'the platform does not automatically clean up old images from the registry' — set retention policies for both app and cache images.
7. For CI runners with NO daemon at all, bypass pack and invoke the CNB lifecycle directly: either the separate phase binaries (analyzer, detector, restorer, builder, exporter) each in an unprivileged container, or the combined `creator` binary which 'runs analyze, detect, restore, build, and export in a single command' (https://buildpacks.io/docs/for-platform-operators/concepts/lifecycle/create/). Tekton's official Buildpacks Phases Task runs the individual lifecycle binaries and explicitly does not use pack; kpack runs buildpacks builds as unprivileged Kubernetes primitives with Secrets/ServiceAccounts for registry auth (https://buildpacks.io/docs/for-platform-operators/how-to/integrate-ci/tekton/, .../kpack/).