Add detailed explanation of React on Rails 16 breaking change

Clarifies that this configuration is a workaround for a regression introduced
in React on Rails v16 where the error handling fallback mechanism was removed.

In v14.2.1, when server bundle lookup failed, it would gracefully fallback to
the Shakapacker output path. This robust error handling was removed in v16.0.1.rc.2
causing the test environment to look in the wrong directory.

The configuration explicitly tells React on Rails where to find bundles in
test environment since the automatic fallback no longer exists.

Author: justin808

config/initializers/react_on_rails.rb

@@ -14,8 +14,14 @@
   # not affect performance.
   config.server_bundle_js_file = "server-bundle.js"
 
-  # React on Rails 16 compatibility: Override generated_assets_dir for test environment
-  # This ensures React on Rails looks in the correct Shakapacker output directory
+  # React on Rails 16 compatibility: Workaround for removed error handling
+  #
+  # BREAKING CHANGE in v16: React on Rails 14.2.1 had robust error handling that would
+  # fallback to the Shakapacker output path when bundle lookup failed. This was removed
+  # in v16.0.1.rc.2, causing it to look in the wrong directory during tests.
+  #
+  # This configuration tells React on Rails where to find bundles in test environment.
+  # Without this, it defaults to public/webpack/test/ instead of public/packs/
   if Rails.env.test?
     config.generated_assets_dir = File.join(Rails.root, "public", "packs")
   end