The CLI is a statically-linked Go binary (CGO_ENABLED=0) that runs on bare
metal with zero dependencies across 10 OS/arch targets. Docker adds no value:

- Auth requires browser OAuth — dead on arrival in a container
- Keyring doesn't work in containers
- Shell completions are useless containerized
- CI/CD has better options (gh release download, curl)
- QEMU multi-arch builds are the slowest part of the release pipeline and
  the source of the timeout-minutes: 30 (now reduced to 15)

Removes: Dockerfile.goreleaser, dockers_v2 from .goreleaser.yaml, QEMU/Buildx/
GHCR steps from release.yml, packages:write permission.