Summary

• Add GCC 13 testing on Linux (CMake only)
• Add MSVC testing on Windows (CMake only)
• Keep Bazel testing with Clang 19 only
• Total of 4 build/test jobs (was 2, now 4)

This will catch cross-compiler compatibility issues (like #61) before they reach users.

Test Plan

• Monitor CI builds to ensure all 4 jobs pass:
  • CMake on Linux with GCC 13
  • CMake on Linux with Clang 19
  • Bazel on Linux with Clang 19
  • CMake on Windows with MSVC