The scout's plan is in the previous task result and the sandbox workspace.
Implement the smallest viable /metrics endpoint:
  - Mount /metrics on the existing HTTP server.
  - Wire one request counter and one in-flight gauge.
  - Add or update one focused test.
Commit on a new branch {{DEMO_SANDBOX_PUSH_BRANCH}}, push it, and open a pull
request using gh inside the sandbox. The sandbox workspace is reused
across turns — your scout's notes are already present.
