clean up AGENTS.md, mostly pointing to other docs (#1935)

* clean up AGENTS.md, mostly pointing to other docs
- Add docs/common/RUNTIME.md - comprehensive guide for runtime development
    (servers, testing, integration tests, debugging)
- Add docs/common/RECIPE_DEV_DEPLOY.md - build, debug, deploy pattern
- Add DEVELOPMENT.md general coding standards, design principles, and best
    practices (removed recipe-specific deployment content)
- Move packages/patterns/README.md -> docs/common/UI_TESTING.md

* switching to promote claude skills but still refer to documents, also is a fallback for other llms

* added INDEX.md for patterns in packages/patterns/

Author: ellyxir