Fixes manual transaction support for local-only collections by adding a utils.acceptMutations(transaction) helper that correctly filters mutations by collection ID and synchronously confirms them so optimistic changes become durable. This resolves cases where manual transactions would silently drop local-only mutations after mutationFn completed, and adds test coverage for mixed/manual-transaction scenarios. Concerns: the new confirmation path writes mutations through sync synchronously and relies on stable collection IDs—calling acceptMutations at the wrong time or misuse across collections could lead to unexpected persistence or ordering/duplication edge cases, so the API needs careful documentation and usage discipline.