EMBED-AND-CI-05: Fail CI on the exit code

What it demonstrates

Letting the CLI’s nonzero exit on error-level findings fail a CI job with no parsing.

Builds on: nothing — this is the first rung of Embed and Automate: the Runner Library and CI Gates.

How it’s done

The declarative YAML artifact, verbatim — no code required.

- name: Validate planning corpus
  run: npx markdown-contract validate docs/planning
  # exit 0 clean, 1 on any error-level finding (fails the step), 2 usage/config error

Surfaces exercised

• CLI validate
• exit-code policy (0/1/2)
• auto-discovered markdown-contract.yaml