Guard cache writes with scope and a version

// before: scope and freshness resolved after the request returns
const doc = await api.get(id);
cache.replace(id, doc);

// after: capture both before awaiting, re-check after
const scope = cache.scope.get();
const seen = writes.get(id) ?? 0;
const doc = await api.get(id);
if (scope !== cache.scope.get() || (writes.get(id) ?? 0) !== seen) return;
cache.replace(id, doc, scope);