Add ghostty terminal emulator and opencode AI coding agent

- Add ghostty (GPU-accelerated terminal emulator) to casks
- Add opencode (AI coding agent for terminal) to formulas

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

install.sh

@@ -107,6 +107,7 @@ FORMULAS=(
   "pinentry-mac"                  # GPG pin entry (required for brew autoupdate --sudo)
   "artginzburg/tap/sudo-touchid"  # Touch ID for sudo
   "gemini-cli"                    # Gemini AI CLI
+  "opencode"                      # AI coding agent
   "ffmpeg"                        # Media processing
   "mas"                           # Mac App Store CLI
   "mole"                          # SSH tunneling
@@ -138,6 +139,7 @@ CASKS=(
   "proton-drive"     # Proton Drive
   "proton-mail"      # Proton Mail
   "protonvpn"        # Proton VPN
+  "ghostty"          # GPU-accelerated terminal emulator
   "claude-code"      # Claude AI coding assistant
   "codex"            # AI coding assistant
   "nova"             # Nova editor