docs: adopt AGENTS.md standard for agent instructions

Rename CLAUDE.md to AGENTS.md to align with the community AGENTS.md
convention (https://agents.md/). This standardized format makes the
repository's agent instructions more discoverable and consistent with
other projects using AI coding assistants.

My real motivation here is I want to support other agentic systems
and not having this project hardcoded to Claude Code, which is proprietary
software.

Assisted-by: Claude Code (Sonnet 4.5)
Signed-off-by: Colin Walters <walters@verbum.org>

Author: cgwalters

.claude/CLAUDE.md

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

CLAUDE.md AGENTS.mdCLAUDE.md renamed to AGENTS.md

@@ -1,6 +1,7 @@
-# CLAUDE.md
+# AGENTS.md
 
-This file provides guidance to Claude Code (claude.ai/code) when working with code in this repository.
+This file implements [https://agents.md/](AGENTS.md) with instructions for coding agents
+when working with code in this repository.
 
 ## Project Overview
 
@@ -10,7 +11,9 @@ The **Ambient Code Platform** is a Kubernetes-native AI automation platform that
 
 ### Amber Background Agent
 
-The platform includes **Amber**, a background agent that automates common development tasks via GitHub Issues. Team members can trigger automated fixes, refactoring, and test additions without requiring direct access to Claude Code.
+The platform includes **Amber**, a background agent that automates common development tasks via GitHub Issues. Team members can trigger automated fixes, refactoring, and test additions without requiring direct access to a specific agentic AI system like Gemini CLI, Goose or Claude Code.
+
+At the current time, the background agent is hardcoded to execute Claude Code.
 
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