Add Hydra experiment configuration example

[cvolkcvolk]

Summary

Add Hydra experiment configuration example

Detailed description

• Build on the typed Maple-table provider introduced by Add typed configurations to Arena environments #858.
• Compose ordered Arena experiments from a required YAML path through EnvironmentRegistry-backed Hydra schemas.
• Keep Experiment-to-Job and typed-Cfg-to-Namespace compatibility adapters explicit at the eval-runner boundary.
• Cover typed composition, invalid input, registry resolution, and sequential simulator execution.