For agents, on top of README.md, which they read first.

• Never add unsafe outside postjevsql-pg. Every other crate is #![forbid(unsafe_code)]; a C surface another crate needs gets a safe wrapper in postjevsql-pg.
• Crates are declared in their BUCK files only. The Cargo.toml files are generated by tools/cargo-gen; never edit one by hand. New crates.io deps go in third-party/Cargo.toml, then re-buckify (chapter 28).
• The jev crates are not here. jev-protocol, jev-client and jev-mock moved to jevcrates on 2026-10-01 and come in through the third-party/jevcrates submodule. Change them there.