Add AGENTS.md and CLAUDE.md for AI coding agent guidance (#15)

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

* Fix inaccuracies in AGENTS.md

- Remove redundant heading that repeats the filename
- Fix incorrect spec/fixtures/ references where that directory doesn't exist
- Fix Claude-specific intro text to be agent-agnostic (pks only)

Co-Authored-By: Claude Sonnet 4.6 (1M context) <noreply@anthropic.com>

---------

Co-authored-by: Claude Sonnet 4.6 (1M context) <noreply@anthropic.com>

Author: dduugg

AGENTS.md

@@ -0,0 +1,27 @@
+This file provides guidance to AI coding agents when working with code in this repository.
+
+## What this project is
+
+`bigrails-redis` is a Redis connection manager for Rails applications that need to manage multiple named Redis connections. It supports connection pooling via [connection_pool](https://github.com/mperham/connection_pool).
+
+## 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 (uses StandardRB, not RuboCop)
+bundle exec standardrb
+bundle exec standardrb --fix  # auto-correct
+```
+
+## Architecture
+
+- `lib/bigrails/redis.rb` — entry point; provides `BigRails::Redis` configuration DSL
+- `lib/bigrails/redis/` — connection registry, per-connection config objects, and Rails railtie for auto-configuration from `config/redis.rb`
+- `spec/` — RSpec tests

CLAUDE.md

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