fix: Auto-remove default gem files to prevent installer conflicts

Automatically detect and remove default bin/dev (Rails) and
config/shakapacker.yml (Shakapacker) files before running the React on
Rails installer. This prevents interactive conflict prompts that would
interrupt the installation process.

The installer now:
- Checks if bin/dev matches the Rails default and removes it if so
- Checks if config/shakapacker.yml matches Shakapacker default and removes it
- Only removes files that exactly match gem defaults (safe deletion)
- Provides user feedback when removing files

This ensures a smooth, non-interactive installation experience while
preserving any customized versions of these files.

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

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

Author: justin808

lib/generators/react_on_rails/install_generator.rb

@@ -38,6 +38,7 @@ class InstallGenerator < Rails::Generators::Base
 
       def run_generators
         if installation_prerequisites_met? || options.ignore_warnings?
+          remove_default_gem_files
           invoke_generators
           add_bin_scripts
           # Only add the post install message if not using Redux
@@ -66,6 +67,53 @@ def print_generator_messages
         GeneratorMessages.messages.each { |message| puts message }
       end
 
+      def remove_default_gem_files
+        remove_default_bin_dev
+        remove_default_shakapacker_yml
+      end
+
+      def remove_default_bin_dev
+        bin_dev_path = File.join(destination_root, "bin/dev")
+        return unless File.exist?(bin_dev_path)
+
+        default_bin_dev = <<~RUBY.strip
+          #!/usr/bin/env ruby
+          exec "./bin/rails", "server", *ARGV
+        RUBY
+
+        current_content = File.read(bin_dev_path).strip
+        return unless current_content == default_bin_dev
+
+        puts Rainbow("🗑️  Removing default bin/dev file to avoid conflicts...").yellow
+        File.delete(bin_dev_path)
+      end
+
+      def remove_default_shakapacker_yml
+        config_path = File.join(destination_root, "config/shakapacker.yml")
+        return unless File.exist?(config_path)
+        return unless shakapacker_yml_matches_default?(config_path)
+
+        puts Rainbow("🗑️  Removing default config/shakapacker.yml file to avoid conflicts...").yellow
+        File.delete(config_path)
+      end
+
+      def shakapacker_yml_matches_default?(config_path)
+        shakapacker_gem_path = Gem.loaded_specs["shakapacker"]&.full_gem_path
+        return false unless shakapacker_gem_path
+
+        default_config_path = File.join(shakapacker_gem_path, "lib/install/config/shakapacker.yml")
+        return false unless File.exist?(default_config_path)
+
+        default_content = File.read(default_config_path)
+        current_content = File.read(config_path)
+
+        current_content == default_content
+      rescue StandardError => e
+        # If we can't compare, don't delete - better safe than sorry
+        puts Rainbow("⚠️  Could not verify shakapacker.yml: #{e.message}").yellow if options.verbose?
+        false
+      end
+
       def invoke_generators
         ensure_shakapacker_installed
         if options.typescript?