docs: publish bilingual teaching README under MIT

[Functionhx]

Summary

• replace the original overview with a visual, teaching-first ActuateX README
• keep Simplified Chinese as the default repository landing page and add a full English companion README with reciprocal language links
• add the standard MIT License for original ActuateX source code and documentation
• clarify that third-party software and the course-supplied TinyMal assets retain their own terms
• add the real three-backend rollout GIF, seven-lab learning path, experiment evidence, code tour, scaling guidance, and roadmap

Validation

• python scripts/verify_repo.py
• python -m compileall -q backends tools scripts
• git diff --check
• npx --yes markdown-link-check README.md --quiet
• npx --yes markdown-link-check README_en.md --quiet