feat(api). 精简了 apis，只保留 Sudoku codec、配置与 mux 的底层接口；
feat(config). 放宽 multiplex 配置要求，支持顶层 multiplex 并兼容原 httpmask.multiplex；multiplex=on 可用于 raw TCP 与 HTTPMask；
fix(mux). 修复慢流阻塞共享 session、流半关闭和并发写入问题，避免其他连接进入 idle 或断流；
perf(httpmask). 为 stream/poll/auto 的 split tunnel 并行预连接，降低 auto 的首次连接 RTT；
perf(codec). 精简 pure、packed 与 poll 热路径的分配和无效代码；
feat(geodata). URL 规则源成功加载后持久缓存；刷新失败时自动使用同 URL 的最后有效缓存；
feat(api). simplified apis to the low-level Sudoku codec, configuration, and mux interfaces;
feat(config). relaxed multiplex placement, supporting top-level multiplex while retaining compatibility with legacy httpmask.multiplex; multiplex=on now works over raw TCP and HTTPMask;
fix(mux). fixed slow streams blocking a shared session, stream half-close behavior, and concurrent writes, preventing unrelated connections from becoming idle or stalled;
perf(httpmask). preconnected split-tunnel requests in parallel for stream/poll/auto, reducing auto first-connection RTT;
perf(codec). reduced allocations and removed ineffective code from the pure, packed, and poll hot paths;
feat(geodata). persistently cached successfully loaded URL rule sources and automatically reused the last valid cache for the same URL when refresh failed;