Framework-agnostic core for Rocket integration (no rocket dependency).
Rocket 集成的框架无关共享层（不依赖 rocket）。
Holds [SaTokenState] / builder and JSON error helpers; re-exports router APIs for bindings.
包含 [SaTokenState] / Builder、JSON 错误体辅助；为重绑定层重导出路由相关 API。