Add Code Agent Prompt Files to TiDB

## Enhancement

To enhance the development experience for TiDB contributors, we propose adding Code Agent prompt files to the TiDB repository. These prompt files will provide developers with basic development commands and tips, such as compilation and testing instructions, directly within their development environment.

### Background:

Code Agents like Claude and other AI assistants can significantly improve developer productivity by providing context-aware suggestions and commands. By creating specific prompt files, we can ensure that these agents are well-equipped to assist with common development tasks in the TiDB project.