Summary

• add a shared builder engine model with buildkit, kaniko, and ci
• let docker-backed services inherit buildDefaults.engine when service config does not set builder.engine
• keep ci on the existing CI build path and limit native builds to buildkit and kaniko

Validation

• pnpm run lint
• BUILD_MODE=yes DATABASE_URL=postgres://user:pass@localhost:5432/lifecycle_test pnpm test
• pnpm run ts-check was run and still fails on existing repository-wide TypeScript errors unrelated to this change

Notes

• test fixtures use neutral sample repositories, pipeline names, and registry values
• the public builder engine schema now accepts only buildkit, kaniko, and ci