feat(development): add Codex and Claude Code CLI tools

- Install Codex and Claude Code on every host
- Document authentication, updates and ChatGPT desktop availability
- Verify both CLI packages build and report their versions

modules/development.nix

@@ -18,6 +18,10 @@
     unzip
     zip
 
+    # Coding assistants; authenticate separately as your normal user.
+    codex
+    claude-code
+
     # Infrastructure, containers, and structured data.
     ansible
     awscli2