Add codex and gemini-cli

- codex (cask): OpenAI coding agent
- gemini-cli (formula): Google Gemini CLI

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

mac_os-config/bin/install_homebrew_casks

@@ -17,5 +17,6 @@ brew install --cask proton-mail
 brew install --cask protonvpn
 
 # Development
+brew install --cask codex
 brew install --cask nova
 brew install --cask transmit

mac_os-config/bin/install_homebrew_formulas

@@ -7,6 +7,9 @@ brew install atuin
 brew install bash
 brew install bash-completion
 
+# AI
+brew install gemini-cli
+
 # Development
 brew install node