Add AGENTS.md and CLAUDE.md for AI coding agent guidance

AGENTS.md

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+This file provides guidance to AI coding agents when working with code in this repository.
+
+## What this project is
+
+`chatwerk` provides an MCP (Model Context Protocol) server built on top of [query_packwerk](https://github.com/rubyatscale/query_packwerk). It lets AI coding assistants (Cursor, Claude, etc.) query packwerk package information, dependencies, and violations from a Ruby codebase.
+
+## Commands
+
+```bash
+bundle install
+
+# Run all tests (RSpec)
+bundle exec rspec
+
+# Run a single spec file
+bundle exec rspec spec/path/to/spec.rb
+
+# Lint
+bundle exec rubocop
+bundle exec rubocop -a  # auto-correct
+```
+
+## Architecture
+
+- `lib/chatwerk.rb` — entry point; starts the MCP server
+- `lib/chatwerk/` — MCP tool definitions that wrap `query_packwerk` queries (e.g. list packs, show violations, show dependencies)
+- `spec/` — RSpec tests

CLAUDE.md

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+@AGENTS.md