Define machine-readable conformance result format

[iHow1]

Context

The reference implementation currently reports 5/5 scenario passes through npm test.

Maintenance task

Publish a stable machine-readable conformance result format so downstream maintainers can consume results without scraping console output.

Proposed output

• conformance/results/schema-v0.json
• runner flag or default artifact: conformance/results/latest.json
• documented fields for scenario id, status, checks, gaps, and runner version

Codex OSS relevance

This is a good Codex-assisted maintainer workflow: review runner output, generate compatibility tests, and check release notes for overclaims.