Fix Windows decode runtime bundling in CI

[seasonyuu]

What changed

• bundle the Windows decode runtime exports required by the runtime bridge
• package the bundled Python runtime and point bundled decode discovery at it on Windows
• pin the Windows CI Python architecture so ARM64 jobs do not link against x64 Python libraries
• keep CI and release bundle validation aligned for the new decode runtime inputs

Validation

• local Windows x64 release build with vcpkg-backed native prerequisites
• local bundle packaging and ools/validate-bundle.py success, including decode list --format json
• GitHub Actions CI run 24871281769 passed on all targets, including Windows x64 and Windows ARM64