feat: 适配 Lua 5.5.1 最新版 (lua_5.5.1 分支)

- lib/lua 替换为 Lua 5.5.1 官方源码(2026-07 发布, 当前最新)
- luaconf.h LUA_EXTRASPACE 扩为 272 字节(与 5.4.8 同方案)
- C API 完全兼容, 桥接层零改动
- PackagePathConfig 测试沿用跨版本语义断言(5.4+ require 返回 loader data 路径)
- 验证: GTest 44/44 通过

lib/lua/lua.hpp

@@ -1,13 +1,10 @@
 // lua.hpp
 // Lua header files for C++
-// <<extern "C">> not supplied automatically because Lua also compiles as C++
-#ifdef __cplusplus
+// 'extern "C" not supplied automatically in lua.h and other headers
+// because Lua also compiles as C++
+
 extern "C" {
-#endif
 #include "lua.h"
 #include "lualib.h"
 #include "lauxlib.h"
-
-#ifdef __cplusplus
 }
-#endif