Update Pro dummy app and docs to use modern Turbo syntax

Address inconsistencies identified in the Turbo migration by updating:

1. Pro version dummy app layout (react_on_rails_pro/spec/dummy/app/views/layouts/application.html.erb):
   - Change 'data-turbolinks-track': true to 'data-turbo-track': 'reload'
   - Ensures consistency with main dummy app which was already updated

2. Documentation (docs/building-features/turbolinks.md):
   - Clarify Turbolinks 5.x vs 2.x syntax differences
   - Add note pointing users to modern Turbo syntax
   - Improve readability of legacy Turbolinks section

These changes complete the Turbo migration across all dummy apps and provide
clearer guidance for users on the recommended modern approach.

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

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

Author: justin808

docs/building-features/turbolinks.md

@@ -128,12 +128,21 @@ This definitely can make an app perform better, even if the JavaScript and style
 1. Include turbolinks via yarn as shown in the [react-webpack-rails-tutorial](https://github.com/shakacode/react-webpack-rails-tutorial/blob/8a6c8aa2e3b7ae5b08b0a9744fb3a63a2fe0f002/client/webpack.client.base.config.js#L22) or include the gem "turbolinks".
 1. Included the proper "track" tags when you include the javascript and stylesheet:
 
+**For Turbolinks 5.x:**
+
 ```erb
   <%= stylesheet_link_tag 'application', media: 'all', 'data-turbolinks-track' => 'reload' %>
   <%= javascript_include_tag 'application', 'data-turbolinks-track' => 'reload' %>
 ```
 
-NOTE: for Turbolinks 2.x, use `'data-turbolinks-track' => true`
+**For Turbolinks 2.x (Classic):**
+
+```erb
+  <%= stylesheet_link_tag 'application', media: 'all', 'data-turbolinks-track' => true %>
+  <%= javascript_include_tag 'application', 'data-turbolinks-track' => true %>
+```
+
+**Note:** If you're using modern Turbo (recommended), use `'data-turbo-track' => 'reload'` instead of `'data-turbolinks-track'`. See the "Using Turbo" section at the top of this document.
 
 1. Add turbolinks to your `application.js` file:
    ```javascript

react_on_rails_pro/spec/dummy/app/views/layouts/application.html.erb

@@ -22,11 +22,11 @@
   </style>
   <%= stylesheet_pack_tag('client-bundle',
                           media: 'all',
-                          'data-turbolinks-track': true) %>
+                          'data-turbo-track': 'reload') %>
 
   <%# Used for testing purposes to simulate hydration failure %>
   <% unless params[:skip_js_packs] == 'true' %>
-    <%= javascript_pack_tag('client-bundle', 'data-turbolinks-track': true, defer: false) %>
+    <%= javascript_pack_tag('client-bundle', 'data-turbo-track': 'reload', defer: false) %>
   <% end %>
   <%= csrf_meta_tags %>
 </head>