Add AGENTS.md documentation for AI tools #8918

Job	Run time
Event File	5s
Build (Linux) (21) / build	11m 43s
Build (macOS) (21, cocoa.macosx.x86_64, macos-15-intel) / build	17m 51s
Build (macOS) (21, cocoa.macosx.aarch64, macos-latest) / build	9m 52s
Build (Windows) (21) / build	14m 41s
	54m 12s

Provide feedback