Darkly’s version — the latest git tag plus the commit height since it
(git describe --tags --long, e.g. v0.3.0-1-gf0c3ea9), baked in by
build.rs as DARKLY_VERSION. The single crate-side home for the version;
consumers read this, never env!("CARGO_PKG_VERSION") (which is the stale
hardcoded Cargo.toml value). See frontend/src/version.ts for the
frontend twin that derives its display version from the same git tags.