Skip version validation when react-on-rails package not installed

The version checker was failing during `rails generate react_on_rails:install`
because it ran after package.json was created by shakapacker:install but before
the generator had a chance to install the react-on-rails package.

Error was:
**ERROR** ReactOnRails: No React on Rails npm package is installed.

This commit adds an additional check to skip validation if neither
react-on-rails nor react-on-rails-pro package is found in package.json,
allowing the generator to complete its installation process.

The validation will still run normally once the packages are installed,
ensuring version compatibility in production apps.

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

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

Author: justin808

lib/react_on_rails/engine.rb

@@ -6,7 +6,7 @@ module ReactOnRails
   class Engine < ::Rails::Engine
     # Validate package versions and compatibility on Rails startup
     # This ensures the application fails fast if versions don't match or packages are misconfigured
-    # Skip validation during installation tasks (e.g., shakapacker:install)
+    # Skip validation during installation tasks (e.g., shakapacker:install, react_on_rails:install)
     initializer "react_on_rails.validate_version_and_package_compatibility" do
       config.after_initialize do
         # Skip validation if package.json doesn't exist yet (during initial setup)
@@ -16,6 +16,13 @@ class Engine < ::Rails::Engine
         # Skip validation when generators explicitly set this flag (packages may not be installed yet)
         next if ENV["REACT_ON_RAILS_SKIP_VALIDATION"] == "true"
 
+        # Skip validation if react-on-rails package is not installed yet (during generator run)
+        # This allows generators to complete before the package is installed
+        node_package_version = VersionChecker::NodePackageVersion.build
+        has_base = node_package_version.react_on_rails_package?
+        has_pro = node_package_version.react_on_rails_pro_package?
+        next unless has_base || has_pro
+
         Rails.logger.info "[React on Rails] Validating package version and compatibility..."
         VersionChecker.build.validate_version_and_package_compatibility!
         Rails.logger.info "[React on Rails] Package validation successful"