The Homebrew formula is named "beads" (not "bd"), so all brew commands
must use `brew install beads` / `brew upgrade beads`. Also removes the
dead update-homebrew job from release.yml — homebrew-core handles
formula updates automatically.
Follows up on #1557 which fixed the Go code in bd doctor.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>