CommonMark 0.31.2 defines block-first parsing, nested block quotes, lazy paragraph continuation, and HTML rendering. The harness runs selected sections via `--pattern`, invokes the supplied program through stdin/stdout, and uses process exit status as the conformance verdict. RESULT: SUCCESS FILES CHANGED: - program SUMMARY: Added the missing executable compatibility entry point. Both block-quote acceptance checks pass; focused tests pass 14/14. BLOCKERS: - None