Enhancement Type

Documentation improvement for AI agents and developers.

Description

Improve AGENTS.md with better testing documentation:

1. Add RealTiKV Tests section: Document how to run tests in tests/realtikvtest/ directory, including:

   • TiUP Playground setup (must run in background)
   • Cluster readiness verification
   • Test execution commands
   • Environment cleanup procedures

2. Improve failpoint guidance: Add clear rules for when to enable failpoint:

   • Check with grep if package uses failpoint
   • Only enable when needed (avoid unnecessary overhead)
   • Provide safe pattern to ensure failpoint is always disabled

3. Remove -v flag from test commands: Avoid excessive log output by default.

Motivation

Help AI agents and developers understand how to properly run different types of tests in TiDB, especially realtikvtest which requires a real TiKV cluster.