Release maintainers

Push tag definitively-vX.Y.Z matching definitively/mix.exs version.

Workflow release-definitively.yml:

1. validate — tag/version check, mix test --cover, mix hex.build
2. build — escript tarballs (linux-x86_64, darwin-arm64)
3. github-release — attach assets + install.sh
4. hex-publish — mix hex.publish --yes (HEX_API_KEY)
5. homebrew-tap-bump — update tap (HOMEBREW_TAP_TOKEN)

Re-run without re-tagging: Actions → Release definitively → Run workflow → enter tag.

Required secrets: HEX_API_KEY, HOMEBREW_TAP_TOKEN (optional until Homebrew automation enabled).