//! Process-lifetime caches for debug environment flags.
//!
//! `std::env::var` takes a global lock and walks `environ` on every call; the
//! structuring pipeline checks debug flags at many decision points, and that
//! showed up as a measurable hotspot (`__findenv_locked` at ~2.4% of samples
//! while rendering `rt.jar`). These flags are process-start configuration, so
//! they are frozen on first use — semantics-preserving.
/// Cached presence check for a debug env flag.
/// Cached parsed value of a debug env flag.