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

Author: dduugg

AGENTS.md

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+# AGENTS.md
+
+This file provides guidance to AI coding agents when working with code in this repository.
+
+## What this project is
+
+`visualize_packs` is a Ruby gem that generates visual diagrams of pack connections in a Rails application using [packs](https://github.com/rubyatscale/packs) and packwerk. It helps teams understand dependency relationships and identify architectural issues.
+
+## Commands
+
+```bash
+bundle install
+
+# Run all tests (RSpec)
+bundle exec rspec
+
+# Run a single spec file
+bundle exec rspec spec/path/to/spec.rb
+
+# Type checking (Sorbet)
+bundle exec srb tc
+```
+
+## Architecture
+
+- `lib/visualize_packs.rb` — entry point; reads pack configuration and produces graph output
+- `lib/visualize_packs/` — core logic: graph building, layout, and rendering (e.g. to DOT/SVG)
+- `spec/` — RSpec tests; `spec/fixtures/` holds sample pack configurations

CLAUDE.md

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+@AGENTS.md