chore(xpkg): add libxpkg 0.0.46

[Sunrisepeak]

Summary

• register mcpplibs.xpkg 0.0.46 for Linux, macOS, and Windows
• use the published openxlings/libxpkg 0.0.46 source archive as GLOBAL
• add the byte-identical mcpp-res/xpkg GitCode asset as CN fallback

Resource verification

• GLOBAL and CN size: 130668 bytes
• SHA256: 6ffbc16108458d47f377ec6046dcf4c67f9a1d3815fc59ea331e39f31906dba0
• two independent GLOBAL downloads matched byte-for-byte
• fresh CN download returned HTTP 200 and matched GLOBAL byte-for-byte

Local validation

• Lua syntax load
• lua5.4 tests/check_mirror_urls.lua pkgs/x/xpkg.lua
• lua5.4 tests/check_package_name.lua pkgs/x/xpkg.lua
• mcpp xpkg parse pkgs/x/xpkg.lua
• git diff --check

Upstream: openxlings/libxpkg#29
Related to openxlings/xlings#381.