docs: add explicit AI-agent-first claim at top of README

Surfaces the agent-tool config files (.cursorrules, .windsurfrules,
copilot-instructions.md, CLAUDE.md, llms.txt) right at the top so any
agent landing here sees the path within seconds.

Author: cschanhniem

README.md

@@ -8,6 +8,8 @@
 
 Not summaries. Not plausible-sounding answers. Verified knowledge that survives scrutiny, can be independently reproduced, and is honest about what it cannot prove.
 
+**AI-agent-first.** Cursor, Windsurf, GitHub Copilot, and Claude Code auto-detect the canonical agent guide in this repo. Any LLM following the [llms.txt](llms.txt) convention finds it too. Read [AGENTS.md](AGENTS.md), then open [tasks-available.json](tasks-available.json) and pick a scoped task.
+
 ---
 
 ## Why This Exists