Cursor AI (.cursorrules) for High-Performance Rust & Tokio Microservices

Act as a Principal Rust Systems Architect. Formulate an uncompromising `.cursorrules` configuration file for a high-throughput async microservice built with Axum 0.8 + Tower + Tokio 1.40 and Tokio. The rules must explicitly instruct Cursor to: 1) Enforce strict zero-cost abstractions, avoiding unnecessary heap allocations and `.clone()` calls, 2) Use `thiserror` for internal domain errors and `anyhow` solely in top-level main binary handlers, 3) Mandate structured logging with `tracing` spans on all public async endpoints, 4) Avoid unconstrained `Arc<Mutex<T>>` in favor of lock-free atomics, channels, or reader-writer locks (`tokio::sync::RwLock`), 5) Include strict linter clippy rules and architectural folder layout directives.