[nitpick] While the reformatting of the runFiles function signature improves readability, this appears to be purely a formatting change unrelated to the main purpose of adding init(). Consider keeping such formatting changes in a separate commit or PR to maintain clearer git history and easier code review.

[nitpick] In the documentation, line 17 states "初期化は非同期に行い、完了する前にreturnしてよいです" (initialization is done asynchronously and may return before completion). This is accurate for the TypeScript runtime's init() implementation which starts async initialization without awaiting. However, consider clarifying that the ready flag should be checked before using the runtime to ensure initialization has completed.

[nitpick] The useEffect has init in its dependency array, but init is a callback that may change on every render depending on its dependencies. This could cause unnecessary re-initialization. Since the README documentation states that "useRuntime() が複数回使われた場合はinitも複数回呼ばれます", this behavior might be intentional, but consider whether this effect should only run once by using an empty dependency array instead.