//! Compile-pass and compile-fail coverage for `#[everruns::tool]` (EVE-829).
//!
//! Pass fixtures prove supported signatures expand and compile; fail fixtures
//! pin the macro's own diagnostics for rejected signatures. The fail fixtures
//! trip the macro's `compile_error!`s (stable text), not downstream type
//! errors, so their `.stderr` is robust across compiler versions.