tools/gen_version_consts.py writes what the pinned client jar's version.json
states (name, id, protocol, data version, pack formats, Java, stable, build
time) into horizon_core::version, and every Rust site reads it from there:
PROTOCOL_VERSION, GAME_VERSION, DATA_VERSION, the save's and the datafixer's
version name, /version, the crash report, the legacy ping, the dedicated
server's start line, the title screens, the default resource folder, the
resource pack format, and the launcher's and horizon-ctl's fallbacks. CI
checks the file against the pinned jar.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>