v2.0.3-ln.1

Downstream release of Simple-WebSocket-Server based on commit de7cb7c39edd6b4178adcc3f5f17d219720b3cdb.

Highlights

• Includes the ScopeRunner TLS cleanup fix.
• Replaces non-trivial thread_local std::unordered_map state with a trivial TLS pointer and intrusive per-thread scope tracking.
• Adds regression coverage for independent runners, self-stop, external stop barriers, non-LIFO unlinking, and repeated thread exits.
• Includes the expanded GCC, Clang, MSVC, MinGW, standalone Asio, Boost.Asio, and ASan/UBSan CI baseline.

No public API changes are included in this release.