component-design-documentation

Review-ready design document for a single component (service / module / library): purpose + context + bounded responsibilities, public interface before internals, collaborators (direction + protocol), data + state machine, errors mapped to external codes, concurrency + ordering, observability hooks, NFR targets (latency / throughput / availability) with strategy, security, config, tests, trade-offs + rejected alternatives, open questions. Hands off to contract / schema / error-strategy / config skills.