Remove immediate_hydration from ReactOnRails configuration

Removes immediate_hydration configuration option from ReactOnRails core.
This feature is now automatically enabled for Pro users and disabled for
non-Pro users without requiring any configuration.

Removed from:
- Default configuration values
- attr_accessor list
- initialize parameters
- initialize assignments

Author: claude

lib/react_on_rails/configuration.rb

@@ -41,8 +41,6 @@ def self.configuration
       components_subdirectory: nil,
       make_generated_server_bundle_the_entrypoint: false,
       defer_generated_component_packs: false,
-      # React on Rails Pro (licensed) feature - enables immediate hydration of React components
-      immediate_hydration: false,
       # Maximum time in milliseconds to wait for client-side component registration after page load.
       # If exceeded, an error will be thrown for server-side rendered components not registered on the client.
       # Set to 0 to disable the timeout and wait indefinitely for component registration.
@@ -64,7 +62,7 @@ class Configuration
                   :server_render_method, :random_dom_id, :auto_load_bundle,
                   :same_bundle_for_client_and_server, :rendering_props_extension,
                   :make_generated_server_bundle_the_entrypoint,
-                  :generated_component_packs_loading_strategy, :immediate_hydration,
+                  :generated_component_packs_loading_strategy,
                   :component_registry_timeout,
                   :server_bundle_output_path, :enforce_private_server_bundles
 
@@ -81,7 +79,7 @@ def initialize(node_modules_location: nil, server_bundle_js_file: nil, prerender
                    same_bundle_for_client_and_server: nil,
                    i18n_dir: nil, i18n_yml_dir: nil, i18n_output_format: nil, i18n_yml_safe_load_options: nil,
                    random_dom_id: nil, server_render_method: nil, rendering_props_extension: nil,
-                   components_subdirectory: nil, auto_load_bundle: nil, immediate_hydration: nil,
+                   components_subdirectory: nil, auto_load_bundle: nil,
                    component_registry_timeout: nil, server_bundle_output_path: nil, enforce_private_server_bundles: nil)
       self.node_modules_location = node_modules_location.present? ? node_modules_location : Rails.root
       self.generated_assets_dirs = generated_assets_dirs
@@ -122,7 +120,6 @@ def initialize(node_modules_location: nil, server_bundle_js_file: nil, prerender
       self.auto_load_bundle = auto_load_bundle
       self.make_generated_server_bundle_the_entrypoint = make_generated_server_bundle_the_entrypoint
       self.defer_generated_component_packs = defer_generated_component_packs
-      self.immediate_hydration = immediate_hydration
       self.generated_component_packs_loading_strategy = generated_component_packs_loading_strategy
       self.server_bundle_output_path = server_bundle_output_path
       self.enforce_private_server_bundles = enforce_private_server_bundles