Fix Zeitwerk eager loading crash in non-Rails environments

Applications were crashing during Zeitwerk eager loading when railtie.rb
references Rails::Railtie in non-Rails contexts. This happened because
Zeitwerk's eager loading occurs before conditional require checks can run.

This fix implements two complementary changes:

1. Wrap the Railtie class definition with a conditional check in railtie.rb
2. Tell Zeitwerk to ignore railtie.rb using loader.ignore()

This ensures the file is only loaded in Rails environments and prevents
NameError crashes during eager loading.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <[email protected]>

Author: trevorturk

lib/ruby_llm/mcp.rb

@@ -100,9 +100,10 @@ def logger
   end
 end
 
-require_relative "mcp/railtie" if defined?(Rails::Railtie)
-
 loader = Zeitwerk::Loader.for_gem_extension(RubyLLM)
+
+loader.ignore("#{__dir__}/mcp/railtie.rb")
+
 loader.inflector.inflect("mcp" => "MCP")
 loader.inflector.inflect("sse" => "SSE")
 loader.inflector.inflect("openai" => "OpenAI")
@@ -118,3 +119,7 @@ def logger
 loader.inflector.inflect("browser_oauth_provider" => "BrowserOAuthProvider")
 
 loader.setup
+
+if defined?(Rails::Railtie)
+  require_relative "mcp/railtie"
+end

lib/ruby_llm/mcp/railtie.rb

@@ -1,11 +1,13 @@
 # frozen_string_literal: true
 
-module RubyLLM
-  module MCP
-    class Railtie < Rails::Railtie
-      generators do
-        require_relative "../../generators/ruby_llm/mcp/install/install_generator"
-        require_relative "../../generators/ruby_llm/mcp/oauth/install_generator"
+if defined?(Rails::Railtie)
+  module RubyLLM
+    module MCP
+      class Railtie < Rails::Railtie
+        generators do
+          require_relative "../../generators/ruby_llm/mcp/install/install_generator"
+          require_relative "../../generators/ruby_llm/mcp/oauth/install_generator"
+        end
       end
     end
   end