m12▌

Design resource creation, cleanup, and scope using RAII, lazy initialization, and pooling patterns. \n \n Covers five lifecycle patterns: RAII with Drop trait, lazy initialization via OnceLock/LazyLock, connection pooling with r2d2/deadpool, guard-based scoped access, and transaction scope boundaries \n Includes decision framework for resource cost, scope determination, and error handling during cleanup \n Provides pattern templates for RAII guards and lazy singletons, plus common errors and ant

Layer 2: Design Choices