Add usage skill for AI agents

.agents/skills/ruby-proxy-headers/SKILL.md

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+---
+name: ruby-proxy-headers
+description: >-
+  Send and receive custom headers during HTTPS CONNECT tunneling in Ruby.
+  Use when integrating proxy headers with Net::HTTP, Faraday, HTTParty, or Excon.
+---
+
+# ruby-proxy-headers
+
+Send custom headers to proxies and receive proxy response headers during HTTPS CONNECT tunneling.
+
+## Installation
+
+```bash
+gem install ruby-proxy-headers
+```
+
+Or in Gemfile:
+
+```ruby
+gem 'ruby-proxy-headers'
+```
+
+Install faraday, httparty, or excon as needed.
+
+## Quick Reference
+
+| Library | Module | Key Methods |
+|---------|--------|-------------|
+| Net::HTTP | `ruby_proxy_headers/net_http` | `patch!`, `proxy_connect_request_headers=` |
+| Faraday | `ruby_proxy_headers/faraday` | `FaradayIntegration.connection` |
+| HTTParty | `ruby_proxy_headers/httparty` | `ProxyHeadersConnectionAdapter` |
+| Excon | `ruby_proxy_headers/excon` | `ExconIntegration.get` (send-only) |
+
+## Usage Patterns
+
+### Net::HTTP
+
+```ruby
+require 'uri'
+require 'openssl'
+require 'ruby_proxy_headers/net_http'
+
+RubyProxyHeaders::NetHTTP.patch!
+
+uri = URI('https://api.ipify.org?format=json')
+proxy = URI(ENV.fetch('PROXY_URL'))
+
+http = Net::HTTP.new(uri.host, uri.port, proxy.host, proxy.port, proxy.user, proxy.password)
+http.use_ssl = true
+
+http.proxy_connect_request_headers = { 'X-ProxyMesh-IP' => '203.0.113.1' }
+
+res = http.request(Net::HTTP::Get.new(uri))
+puts http.last_proxy_connect_response_headers['X-ProxyMesh-IP']
+```
+
+Call `RubyProxyHeaders::NetHTTP.patch!` once before creating connections.
+
+### Faraday
+
+```ruby
+require 'ruby_proxy_headers/faraday'
+
+conn = RubyProxyHeaders::FaradayIntegration.connection(
+  proxy: ENV.fetch('PROXY_URL'),
+  proxy_connect_headers: { 'X-ProxyMesh-Country' => 'US' }
+)
+
+res = conn.get('https://api.ipify.org?format=json')
+puts res.headers['X-ProxyMesh-IP']
+```
+
+### HTTParty
+
+```ruby
+require 'httparty'
+require 'ruby_proxy_headers/httparty'
+
+RubyProxyHeaders::NetHTTP.patch!
+
+proxy = URI(ENV.fetch('PROXY_URL'))
+HTTParty.get(
+  'https://api.ipify.org?format=json',
+  http_proxyaddr: proxy.host,
+  http_proxyport: proxy.port,
+  http_proxyuser: proxy.user,
+  http_proxypass: proxy.password,
+  proxy_connect_request_headers: { 'X-ProxyMesh-IP' => '203.0.113.1' },
+  connection_adapter: RubyProxyHeaders::ProxyHeadersConnectionAdapter
+)
+
+puts RubyProxyHeaders.proxy_connect_response_headers['X-ProxyMesh-IP']
+```
+
+### Excon (send-only)
+
+Excon supports sending headers on CONNECT but does not expose CONNECT response headers.
+
+```ruby
+require 'ruby_proxy_headers/excon'
+
+RubyProxyHeaders::ExconIntegration.get(
+  'https://api.ipify.org?format=json',
+  proxy_url: ENV.fetch('PROXY_URL'),
+  proxy_connect_headers: { 'X-ProxyMesh-Country' => 'US' }
+)
+```
+
+## Reading Response Headers
+
+- **Net::HTTP**: `http.last_proxy_connect_response_headers`
+- **Faraday**: Merged into `response.headers`
+- **HTTParty**: `RubyProxyHeaders.proxy_connect_response_headers` (thread-local)
+
+## Proxy Headers
+
+Custom headers sent during CONNECT are proxy-specific. Check your proxy provider's docs.
+
+Example with [ProxyMesh](https://proxymesh.com):
+
+| Header | Direction | Purpose |
+|--------|-----------|---------|
+| `X-ProxyMesh-Country` | Send | Route through specific country |
+| `X-ProxyMesh-IP` | Send/Receive | Request or receive sticky IP |
+
+## Testing
+
+```bash
+export PROXY_URL='http://user:pass@proxy.example.com:8080'
+bundle exec ruby test/test_proxy_headers.rb -v
+```