Release superthread

Bump version → commit → rake release → GitHub Actions handles the rest (gem build, GitHub Release, Homebrew formula).

Workflow

1. Review unreleased changes

ruby -r ./lib/superthread/version -e 'puts Superthread::VERSION'
git log v<CURRENT_VERSION>..HEAD --oneline

Summarize changes and recommend a bump: major (breaking), minor (new features), or patch (fixes/docs).

2. Draft release notes

Write concise, user-facing notes. Group under ### Added, ### Changed, ### Fixed, ### Removed as appropriate. Show the draft to the user for confirmation.