melange and apko configuration reference

Schema references: melange (github.com/chainguard-dev/melange, docs/md/melange.md); apko (github.com/chainguard-dev/apko, docs/apko_file.md).

• copyright (melange) is a list under package; each entry has license (required, SPDX), paths (default *), attestation, license-path, and detection-override.
• Template variables: ${{targets.destdir}} resolves to /home/build/melange-out/<package.name>, where installed files must land; ${{package.version}}; also package.name, package.epoch, package.full-version, targets.outdir, targets.contextdir, targets.subpkgdir.
• apko has no ports or EXPOSE field; declare ports in your orchestrator.
• Setting Linux file capabilities is a melange feature via the setcap field (path, add, reason); apko has no capabilities field.
• File permissions and ownership: in apko use the paths field (path, type, uid, gid, permissions such as 0o755, recursive). In melange there is no dedicated field; use chmod, chown, or install in pipeline runs: steps writing into ${{targets.destdir}}.
• There is no melange cache clean command; clear the cache by deleting the --cache-dir directory (default ./melange-cache/).