[REQ] Modernize Copacetic build workflows

[robert-cronin]

What kind of request is this?

Improvement of existing experience

What is your request or suggestion?

Copacetic’s current CLI orchestrates BuildKit directly and implements its own image export logic.
That’s extra code to maintain and it blocks simple “docker build” users from patching images.
This issue tracks two complementary ways to clean that up:

1. copa generate streaming tar where something like copa generate -i ubuntu:22.04 -t patched | docker build - works out of the box. This should be the easiest approach.
2. A native BuildKit frontend where we publish ghcr.io/project‑copacetic/copacetic‑frontend:<ver> so users can run something like:

buildctl build \
 --frontend=gateway.v0 \
 --opt source=ghcr.io/project‑copacetic/copacetic‑frontend:latest \
 --opt image=docker.io/library/alpine:3.14.0 \
 --output type=image,name=localhost:5000/alpine:3.14.0-patched,push=true \
 --progress=plain

Are you willing to submit PRs to contribute to this feature request?

• Yes, I am willing to implement it.

[github-actions]

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