Add RBS type signatures for Dev module classes

This commit adds comprehensive RBS type signatures for all classes
in the `lib/react_on_rails/dev/` module and updates the Steepfile to
enable type checking for these files.

Files added:
- sig/react_on_rails/dev/file_manager.rbs
- sig/react_on_rails/dev/pack_generator.rbs
- sig/react_on_rails/dev/process_manager.rbs
- sig/react_on_rails/dev/server_manager.rbs

Why this matters:
The recent NameError in PackGenerator (uninitialized constant
ReactOnRails::PackerUtils) highlighted that these files weren't being
type-checked. While RBS/Steep cannot catch missing require statements
or load order issues, having type signatures for these classes will:

1. Catch type-related errors during development
2. Provide better IDE autocomplete and documentation
3. Ensure method signatures match their implementations
4. Prevent future type-related regressions

Note: RBS validation passes. Steep shows some warnings for external
constants (Rails, Rake, Shakapacker) which is expected for files that
integrate with external frameworks.

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

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

Author: justin808

Steepfile

@@ -28,6 +28,10 @@ target :lib do
   check "lib/react_on_rails.rb"
   check "lib/react_on_rails/configuration.rb"
   check "lib/react_on_rails/controller.rb"
+  check "lib/react_on_rails/dev/file_manager.rb"
+  check "lib/react_on_rails/dev/pack_generator.rb"
+  check "lib/react_on_rails/dev/process_manager.rb"
+  check "lib/react_on_rails/dev/server_manager.rb"
   check "lib/react_on_rails/git_utils.rb"
   check "lib/react_on_rails/helper.rb"
   check "lib/react_on_rails/packer_utils.rb"

sig/react_on_rails/dev/file_manager.rbs

@@ -0,0 +1,15 @@
+module ReactOnRails
+  module Dev
+    class FileManager
+      def self.cleanup_stale_files: () -> bool
+
+      private
+
+      def self.cleanup_overmind_sockets: () -> bool
+      def self.cleanup_rails_pid_file: () -> bool
+      def self.overmind_running?: () -> bool
+      def self.process_running?: (Integer) -> bool
+      def self.remove_file_if_exists: (String, String) -> bool
+    end
+  end
+end

sig/react_on_rails/dev/pack_generator.rbs

@@ -0,0 +1,19 @@
+module ReactOnRails
+  module Dev
+    class PackGenerator
+      def self.generate: (?verbose: bool) -> void
+
+      private
+
+      def self.run_pack_generation: (?silent: bool) -> bool
+      def self.should_run_directly?: () -> bool
+      def self.rails_available?: () -> bool
+      def self.run_rake_task_directly: (?silent: bool) -> bool
+      def self.load_rake_tasks: () -> void
+      def self.prepare_rake_task: () -> untyped
+      def self.capture_output: (bool) { () -> bool } -> bool
+      def self.handle_rake_error: (Exception, bool) -> void
+      def self.run_via_bundle_exec: (?silent: bool) -> (bool | nil)
+    end
+  end
+end

sig/react_on_rails/dev/process_manager.rbs

@@ -0,0 +1,22 @@
+module ReactOnRails
+  module Dev
+    class ProcessManager
+      VERSION_CHECK_TIMEOUT: Integer
+
+      def self.installed?: (String) -> bool
+      def self.ensure_procfile: (String) -> void
+      def self.run_with_process_manager: (String) -> void
+
+      private
+
+      def self.installed_in_current_context?: (String) -> bool
+      def self.version_flags_for: (String) -> Array[String]
+      def self.run_process_if_available: (String, Array[String]) -> bool
+      def self.run_process_outside_bundle: (String, Array[String]) -> bool
+      def self.process_available_in_system?: (String) -> bool
+      def self.with_unbundled_context: () { () -> untyped } -> untyped
+      def self.show_process_manager_installation_help: () -> void
+      def self.valid_procfile_path?: (String) -> bool
+    end
+  end
+end

sig/react_on_rails/dev/server_manager.rbs

@@ -0,0 +1,39 @@
+module ReactOnRails
+  module Dev
+    class ServerManager
+      type mode = :development | :production_like | :static | :hmr
+
+      def self.start: (mode, String?, ?verbose: bool, ?route: String?, ?rails_env: String?) -> void
+      def self.kill_processes: () -> void
+      def self.development_processes: () -> Hash[String, String]
+      def self.kill_running_processes: () -> bool
+      def self.find_process_pids: (String) -> Array[Integer]
+      def self.terminate_processes: (Array[Integer]) -> void
+      def self.kill_port_processes: (Array[Integer]) -> bool
+      def self.find_port_pids: (Integer) -> Array[Integer]
+      def self.cleanup_socket_files: () -> bool
+      def self.print_kill_summary: (bool) -> void
+      def self.show_help: () -> void
+      def self.run_from_command_line: (?Array[String]) -> void
+
+      private
+
+      def self.help_usage: () -> String
+      def self.help_commands: () -> String
+      def self.help_options: () -> String
+      def self.help_customization: () -> String
+      def self.help_mode_details: () -> String
+      def self.help_troubleshooting: () -> String
+      def self.run_production_like: (?_verbose: bool, ?route: String?, ?rails_env: String?) -> void
+      def self.run_static_development: (String, ?verbose: bool, ?route: String?) -> void
+      def self.run_development: (String, ?verbose: bool, ?route: String?) -> void
+      def self.print_server_info: (String, Array[String], ?Integer, ?route: String?) -> void
+      def self.print_procfile_info: (String, ?route: String?) -> void
+      def self.procfile_port: (String) -> Integer
+      def self.box_border: (Integer) -> String
+      def self.box_bottom: (Integer) -> String
+      def self.box_empty_line: (Integer) -> String
+      def self.format_box_line: (String, Integer) -> String
+    end
+  end
+end