feat(claude): add AGENTS.md shim rule and repo-root CLAUDE.md (#64)

Adds a global Claude Code rule (~/.claude/rules/agents-shim.md) that
fires when CLAUDE.md is in context, redirecting instructions to
AGENTS.md. Also adds a repo-root CLAUDE.md containing @AGENTS.md.

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

Author: ChipWolf

CLAUDE.md

@@ -0,0 +1 @@
+@AGENTS.md

home/dot_claude/rules/agents-shim.md

@@ -0,0 +1,7 @@
+---
+paths:
+  - "**/CLAUDE.md"
+---
+
+Put instructions in `AGENTS.md`, not `CLAUDE.md`.
+`CLAUDE.md` should only ever contain `@AGENTS.md`.