Offline-First Optimistic Mutation Queue with Rollback & State Reconciliation

### Problem Overview Modern apps (Linear, Notion, Superhuman) give instantaneous UI feedback by applying mutations optimistically before server confirmation. If the server rejects a change, the UI must rollback without overwriting newer concurrent user edits. Build an **Optimistic Mutation Engine** supporting snapshot rollbacks and conflict resolution. ### Functional Requirements 1. **`mutate<T>(mutation: MutationConfig<T>): Promise<T>`**: - Takes current state, creates an immutable rollback snapshot, immediately applies `optimisticUpdater(state)`, and fires network request. 2. **Rollback on Server Error**: - If network call fails, reverts state back accurately while preserving un-related mutations applied concurrently. 3. **Sequential Replay of Offline Mutations**: - If device is offline, mutations queue up in order. When connectivity resumes, replays mutations sequentially. 4. **Conflict Resolution Strategy**: - Supports **Last-Write-Wins (LWW)** and custom `resolveConflict(local, remote)` resolvers. ### Non-Functional Requirements - **State Immutability**: Guarantee state is never directly mutated in place. - **Transactional Consistency**: Partial failures must not corrupt the state tree.