FreeLang v11 런타임의 yield 의미론을 공식 invariant로 문서화. 5개 핵심 invariant: (1) long-running loop must yield, (2) blocking sleep forbidden in async path, (3) single reader owns progression, (4) callback execution requires scheduler progression, (5) pending resolution only after yield opportunity. Scheduler Tick Model 포함: yield→tick→IO callback→pending→timer 순서 명시. FreeDoc 형식으로 작성.