chore(ci): improve GitHub Actions workflows for cross-platform builds

[fbraz3]

This PR consolidates improvements to the CI/CD pipeline from the windows-sdl development branch:

Modern workflow improvements:

• Rewrite CI pipeline for GeneralsX cross-platform builds
• Archive legacy SuperHackers workflows to .github/workflows/old/
• Add workflow validation and documentation

build-linux.yml enhancements:

• Add libvulkan-dev to dependencies (required for DXVK)
• Pin vcpkg to specific commit for reproducible builds
• Simplify bundle layout: copy all .so files to root (no lib/ subdir)
• Add OpenAL library bundling (openal_soft build output)
• Add validation checks for required runtime libraries:
  • libgamespy.so*
  • libdxvk_d3d8.so*
  • libSDL3.so*
  • libopenal.so*
• Create archive (.tar.gz) of runtime bundle for better packaging
• Improve bundle diagnostics and logging

build-macos.yml enhancements:

• Update vcpkg commit to match linux workflow (reproducible builds)

ci.yml improvements:

• Consolidated workflow template for both Generals and GeneralsXZH

Scope:

• Excludes Windows (build-windows.yml) - TBD for future modernization
• Focuses only on CI/CD improvements (no game logic changes)
• Maintains backward compatibility with existing build artifacts