Remove unnecessary using_packer? check since Shakapacker is required

- Since gemspec requires Shakapacker, the using_packer? check is redundant
- Simplifies bundle_js_file_path logic by removing unnecessary condition
- Inverts condition structure for better readability per RuboCop
- Maintains exact same functionality with cleaner code

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

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

Author: justin808

lib/react_on_rails/utils.rb

@@ -72,13 +72,13 @@ def self.bundle_js_file_path(bundle_name)
       # Priority order depends on bundle type:
       # SERVER BUNDLES (normal case): Try secure non-public locations first, then manifest, then legacy
       # CLIENT BUNDLES (normal case): Try manifest first, then fallback locations
-      if ReactOnRails::PackerUtils.using_packer? && bundle_name != "manifest.json"
-        bundle_js_file_path_with_packer(bundle_name)
-      else
+      if bundle_name == "manifest.json"
         # Default to the non-hashed name in the specified output directory, which, for legacy
         # React on Rails, this is the output directory picked up by the asset pipeline.
         # For Shakapacker, this is the public output path defined in the (shaka/web)packer.yml file.
         File.join(generated_assets_full_path, bundle_name)
+      else
+        bundle_js_file_path_with_packer(bundle_name)
       end
     end