Set up Cursor Cloud dev environment (AGENTS.md)

[vistone]

Summary

Sets up and verifies the development environment for the fingerprint-rust Rust workspace, and documents durable, non-obvious setup/run guidance for future cloud agents in a new AGENTS.md.

No application code was changed — only AGENTS.md was added.

Environment

• Rust 1.90.0 (pinned via rust-toolchain.toml).
• System deps installed in the VM: pkg-config, libssl-dev (required by openssl-sys), redis-server (for the optional gateway).
• Update script: cargo fetch (minimal, idempotent dependency refresh).

Verified (core product — Rust workspace)

• ✅ cargo build (default members)
• ✅ cargo fmt --all -- --check
• ✅ cargo clippy --workspace --all-targets (0 warnings)
• ✅ cargo test --workspace --lib (all crates pass, 0 failures)
• ✅ Hello-world: cargo run -p fingerprint-core --example modern_fingerprinting (JA4 TLS / JA4X X.509 / PQC / WASM fingerprint generation)

Optional service

• ✅ fingerprint-gateway compiles, boots, binds :8080, connects to Redis.
• ⚠️ Pre-existing app bug: run_server wraps Arc<RateLimiter>/Arc<ApiKeyValidator> in web::Data, so handlers extracting web::Data<RateLimiter>/web::Data<ApiKeyValidator> can't resolve app data and every route returns HTTP 500. This is application code, not environment setup, so it is left as-is and documented in AGENTS.md.

Notes

• Root examples/ dir is not a compiled Cargo target; examples live in individual crates (run via -p <crate> --example <name>).
• phase7_api/ Python FastAPI service is optional and needs uncommitted .pkl models for real inference.