New Sub Agents support

Claude code version v1.0.60 added support for [sub agents](https://docs.anthropic.com/en/docs/claude-code/sub-agents).

I've tried to make the action use one of the agents defined in my project but it does not seem to work.

**Are the agents not yet available on the github action?**

The same goes for slash commands, there i came to the conclusion that it's better to embed custom prompts in the github action, but sub agents would be very useful!