fix: replace Unix-only clean and sync-readme scripts with cross-platform Node.js equivalents

[buer5]

PR 3: fix/windows-clean-script

Summary

• Replace rm -rf in root package.json clean script with node -e using fs.rmSync({ recursive: true, force: true }).
• Replace cp in sync-readme script with node -e using fs.copyFileSync.

Why

The clean and sync-readme scripts use Unix-only commands (rm -rf, cp) that fail on Windows PowerShell/CMD, blocking Windows developers from running local builds and cleanups.

Tests

npm run clean
npm run sync-readme
npm run build
npm test

Note

Uses only Node.js built-in fs module — no third-party dependencies like rimraf needed. Works identically on macOS, Linux, and Windows.