feat: Add CLAUDE_CODE_VERSION build arg to devcontainer.json

- Add CLAUDE_CODE_VERSION with default value of "latest" as a build argument
- Allows overriding Claude Code version during devcontainer build

🤖 Generated with [Claude Code](https://claude.ai/code)

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

.devcontainer/devcontainer.json

@@ -3,7 +3,8 @@
   "build": {
     "dockerfile": "Dockerfile",
     "args": {
-      "TZ": "${localEnv:TZ:America/Los_Angeles}"
+      "TZ": "${localEnv:TZ:America/Los_Angeles}",
+      "CLAUDE_CODE_VERSION": "latest"
     }
   },
   "runArgs": [