docs(agents): point agents to CLAUDE.md for Claude review context

Adds a cross-reference so any agent (not just Claude) knows to look at
CLAUDE.md when it exists for review or deep-dive background.

Signed-off-by: Aaron D. Lee <himself@adlee.work>

AGENTS.md

@@ -10,6 +10,17 @@ This file orients any agent (human, AI, hybrid) working in the repo.
 
 ---
 
+## Context files for agents
+
+- **`AGENTS.md`** (this file) — shared orientation: project structure, build/test commands,
+  code style, git workflow, and multi-agent coordination rules.
+- **`CLAUDE.md`** — optional companion used when Claude is brought in for review or
+  deep-dive context. All agents, including future Claude sessions, should check
+  `CLAUDE.md` when available for extra background before resuming a task or acting
+  on review feedback.
+
+---
+
 ## Project structure (current + planned)
 
 ```