chore: cleanup workflows and add release binary testing

- Remove 4 unused workflows (experimental-macos, express-release, mlx-apple-silicon, update-changelog)
- Add test-release-binaries.yml to test pre-built release artifacts
- Downloads binaries from GitHub releases instead of rebuilding
- Tests all 5 platforms: Linux x64/ARM64, Windows x64, macOS Intel/ARM64

Author: Michael-A-Kuykendall