Summary

• add a dedicated GitHub Actions workflow that publishes GoReleaser nightlies on every push to main
• configure GoReleaser to keep a single rolling prerelease tagged nightly with predictable nightly versioning
• document the required GoReleaser Pro secret and the intentional Homebrew skip for nightly runs

Validation

• go test ./...
• git diff --check
• local goreleaser check could not validate the nightly stanza because the available fallback is the OSS binary and nightly is a GoReleaser Pro feature

Closes #230