ci: make Homebrew tap publish best effort

[cbusillo]

Summary

• make Homebrew tap publishing best-effort when the cross-repo token cannot push to just-every/homebrew-tap
• keep generating the formula, but warn and continue so GitHub Release/npm publishing is not blocked by tap credential configuration
• preserve a clear warning pointing at GH_PAT cross-repo write access

Validation

• ruby -e 'require "yaml"; YAML.load_file(".github/workflows/release.yml"); puts "yaml ok"'\n- git diff --check\n- ./build-fast.sh\n\nRefs Fix release preflight runner capabilities #108\nRefs Plan Every Code default branch and release identity #87