Fix CI failure by skipping version validation during generator runtime

The strict version validation added in #1881 runs during Rails initialization
via an after_initialize hook. However, when running `rails generate react_on_rails:install`,
the npm packages haven't been installed yet, causing the validation to fail with:
"No React on Rails npm package is installed."

This fix adds a check to skip validation when running Rails generators (detected by
checking if ARGV.first is "generate" or "g"). The generator will install packages
during its execution, so validation at initialization time is not appropriate.

This allows CI to successfully run example generation tasks without errors.

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

Co-Authored-By: Claude <noreply@anthropic.com>

Author: justin808

lib/react_on_rails/engine.rb

@@ -6,9 +6,13 @@ 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) or generator runtime
     initializer "react_on_rails.validate_version_and_package_compatibility" do
       config.after_initialize do
+        # Skip validation when running Rails generators - they will install packages during execution
+        running_generator = ARGV.first == "generate" || ARGV.first == "g"
+        next if running_generator
+
         # Skip validation if package.json doesn't exist yet (during initial setup)
         package_json = VersionChecker::NodePackageVersion.package_json_path
         next unless File.exist?(package_json)