Improve Python package onboarding

[bigboateng]

Summary

• replace the Python package description with a tested five-step onboarding guide
• generate public PyPI requirements for new Python workflows
• keep npm and PyPI package banners registry-specific while retaining both on GitHub
• make root README links stable when rendered on npm

Verification

• npm run test:release
• go test ./... and go vet ./...
• Python, TypeScript, and Rust SDK tests
• 40 example workflows and 8 runtime evaluation checks
• six candidate Python wheels passed release inspection and twine check
• clean wheel install completed the documented environment-doctor workflow