Add runlet to AI and Agents / Orchestration

[DMIAOCHEN]

What is this project?

runlet - A tiny observable runtime for Python agents.

• Provider-neutral — works with any LLM provider
• Zero required dependencies
• MIT licensed
• Available on PyPI: pip install runlet

Checklist

• Only one project in this PR
• Entry is in alphabetical order within its category
• Use PyPI package name as display name
• GitHub repo URL used
• Description ends with a period