[codex] Data-drive Homebrew installers

[mcclayton]

Summary

• Replace repeated Homebrew package and cask install calls with list-driven helpers.
• Remove the old string-command installPackage path and make zsh use the Homebrew helper.
• Add installer helper tests, a reusable Docker start smoke script, and the complete-pattern-adoption tenet.

Validation

• bash ./ci/checks.sh
• bash ./ci/docker_start_smoke.sh vim-modern
• git diff --check