Implements lazy async pipeline operators (map, flatMap, chunk, toArray) using Web Streams API. The chunk operator with size+deadline is a non-obvious pattern for batching with timeout. This module is self-contained and could be extracted as a standalone streaming utility library.

Provides a composable middleware system for command handlers with before/after hooks, decision-level middleware, and built-in operators (append, skip, stop, reject). Demonstrates a clean separation of cross-cutting concerns (validation, authorization, logging) from business logic. The pattern is reusable in any command-processing pipeline.

Implements a BDD-style given/when/then specification for testing decider-based business logic. Supports both sync and async deciders, error assertions, and event stream verification. This pattern is reusable for any event-sourced domain and can be extracted as a standalone testing utility.

A fully functional in-memory event store implementing the EventStore interface with optimistic concurrency, stream reading, and after-commit hooks. Designed for fast unit tests without external dependencies. The implementation is self-contained and demonstrates a clean contract that can be reused as a reference for custom event store implementations.