home: add claude-code program with home-manager module

Configures claude-code using the home-manager programs.claude-code module:
- Settings: model, gopls plugin, auto-update disabled, permissions
- Agents: docs-verifier, security-reviewer
- Skills: pr summary generator

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

home/hosts/gunter/default.nix

@@ -28,6 +28,7 @@
           ../../programs/rofi
           ../../programs/streamcontroller
           ../../programs/tmux
+          ../../programs/claude-code
           ../../programs/vscode
           ../../scripts
           ../../services/backup-home.nix