toolchain router.
  /freertos/mcp            - MCP, Streamable HTTP (authed)
  /freertos/docs           - tool catalog
  /freertos/files/download - stream a file off the pod (authed)
  /freertos/files/upload   - stream a file onto the pod (authed)
  /freertos/session/reset  - recycle the caller's pod (authed)
  /healthz                    - liveness
  /readyz                     - readiness