Use default loading strategy based on Shakapacker version

The previous fix explicitly set generated_component_packs_loading_strategy
to :async, which broke CI for minimum dependencies (Shakapacker 6.0).

Root cause:
- Commit ee80bc2 changed main bundle to use async: true
- Original config had :defer explicitly set, causing race condition
- Setting :async explicitly breaks Shakapacker < 8.2.0

Solution:
- Remove explicit configuration setting
- Let it default based on Shakapacker version:
  - Shakapacker >= 8.2.0: defaults to :async (optimal)
  - Shakapacker < 8.2.0: defaults to :sync (compatible)
- Update test to check for version-appropriate default

This fixes both the original race condition AND maintains compatibility
with minimum supported dependencies.

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

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

Author: justin808

spec/dummy/config/initializers/react_on_rails.rb

@@ -42,5 +42,7 @@ def self.adjust_props_for_client_side_hydration(component_name, props)
   config.components_subdirectory = "startup"
   config.auto_load_bundle = true
   config.immediate_hydration = false
-  config.generated_component_packs_loading_strategy = :async
+  # Don't explicitly set generated_component_packs_loading_strategy - let it default based on Shakapacker version
+  # - Shakapacker >= 8.2.0: defaults to :async (optimal performance)
+  # - Shakapacker < 8.2.0: defaults to :sync (compatibility)
 end

spec/dummy/spec/helpers/react_on_rails_helper_spec.rb

@@ -77,7 +77,14 @@ def self.pro_attribution_comment
       allow(helper).to receive(:append_stylesheet_pack_tag)
       expect { helper.load_pack_for_generated_component("component_name", render_options) }.not_to raise_error
 
-      expect(helper).to have_received(:append_javascript_pack_tag).with("generated/component_name", { defer: true })
+      # Expect the default loading strategy based on Shakapacker version
+      if ReactOnRails::PackerUtils.supports_async_loading?
+        expect(helper).to have_received(:append_javascript_pack_tag).with("generated/component_name",
+                                                                          { defer: false, async: true })
+      else
+        # When async is not supported, defaults to :sync which means { defer: false }
+        expect(helper).to have_received(:append_javascript_pack_tag).with("generated/component_name", { defer: false })
+      end
       expect(helper).to have_received(:append_stylesheet_pack_tag).with("generated/component_name")
     end