Add service health checks for the end-to-end pipeline

[aria-agentworks]

Summary

Add health checks for the Brain, Hands, and Mouth services so operators can see which part of the pipeline is degraded before running jobs.

Why this matters

The repository combines multiple moving parts. Basic health reporting will make the system easier to debug and safer to operate.

Proposed work

• Define health endpoints or probes for each service
• Surface service status in the dashboard or API
• Document the expected response shape
• Fail fast when a critical dependency is unavailable

Acceptance criteria

• Operators can view service readiness before pipeline execution
• The dashboard or API exposes a clear degraded state
• Local docs explain how to verify health checks manually