Improve RBS signatures based on code review feedback

- Fix Utils module method signatures:
  - Remove question mark from rails_version_less_than (matches actual implementation)
  - Add missing public utility methods:
    - react_on_rails_pro_version
    - rsc_support_enabled?
    - full_text_errors_enabled?
    - smart_trim
    - find_most_recent_mtime
    - prepend_to_file_if_text_not_present
    - detect_package_manager
    - default_troubleshooting_section
    - server_bundle_js_file_path
    - source_path
    - public_bundles_full_path
    - generated_assets_full_path
    - gem_available?

- Add missing Configuration private methods:
  - rsc_bundle_js_file
  - react_client_manifest_file
  - react_server_client_manifest_file

These methods are used in ensure_webpack_generated_files_exists and other
parts of the codebase, so including them improves type coverage.

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

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

Author: justin808

sig/react_on_rails/configuration.rbs

@@ -89,5 +89,8 @@ module ReactOnRails
     def configure_skip_display_none_deprecation: () -> void
     def raise_missing_components_subdirectory: () -> void
     def compile_command_conflict_message: () -> String
+    def rsc_bundle_js_file: () -> String?
+    def react_client_manifest_file: () -> String?
+    def react_server_client_manifest_file: () -> String?
   end
 end

sig/react_on_rails/utils.rbs

@@ -10,10 +10,22 @@ module ReactOnRails
     def self.server_bundle_path_is_http?: () -> bool
     def self.bundle_js_file_path: (String bundle_name) -> String
     def self.react_on_rails_pro?: () -> bool
-    def self.server_bundle?: (String bundle_name) -> bool
+    def self.react_on_rails_pro_version: () -> String?
+    def self.rsc_support_enabled?: () -> bool
+    def self.full_text_errors_enabled?: () -> bool
+    def self.smart_trim: (String str, ?Integer max_length) -> String
+    def self.find_most_recent_mtime: (Array[String] files) -> Time?
+    def self.prepend_to_file_if_text_not_present: (file: String, text_to_prepend: String, regex: Regexp) -> void
+    def self.detect_package_manager: () -> String
+    def self.default_troubleshooting_section: () -> String
+    def self.server_bundle_js_file_path: () -> String
     def self.running_on_windows?: () -> bool
-    def self.rails_version_less_than?: (String version) -> bool
+    def self.rails_version_less_than: (String version) -> bool
     def self.rails_version_less_than_4_1_1?: () -> bool
+    def self.source_path: () -> String
+    def self.public_bundles_full_path: () -> String
+    def self.generated_assets_full_path: () -> String
+    def self.gem_available?: (String name) -> bool
 
     module Required
       def required: (String name) -> untyped