docs: update contributor setup instructions

[liangmiQwQ]

• List contributor prerequisites and recommend Vite+ for managing Node.js and pnpm on macOS, Linux, and Windows.
• Replace stacked PR guidance with small, focused PRs that work for fork contributors.
• Remove the verified-commit section, including instructions to re-sign commits and force-push.
• Move release and recovery instructions to MAINTENANCE.md and local registry implementation details to packages/tools/README.md.
• Simplify local testing instructions and link to the existing global CLI installation steps.

🤖 Generated with Codex