docs: add Claude Code to documented AI coding agents

Claude Code was already installed via npm (line 65 of Dockerfile) but
was missing from the feature lists in README.md and CLAUDE.md.

Generated with [Claude Code](https://claude.ai/code)
via [Happy](https://happy.engineering)

Co-Authored-By: Claude <noreply@anthropic.com>
Co-Authored-By: Happy <yesreply@happy.engineering>

README.md

@@ -5,8 +5,7 @@
 A containerized cloud development environment with web-based GUI access, featuring:
 - **VSCode or Google Antigravity** via browser-based VNC (port 5800)
 - **SSH access** option (OpenSSH on port 22, additive with any IDE)
-- **Happy Coder** AI assistant backed by Claude
-- **OpenCode** and **Crush** open-source AI coding agents (terminal-based)
+- **Claude Code**, **Happy Coder**, **OpenCode**, and **Crush** AI coding agents (terminal-based)
 - **Automatic GitHub repo cloning** on startup
 - **Persistent home directory** via ReadWriteMany PVC
 - **Kubernetes-native** Helm chart deployment