feat(runtime): integrate settings service boundary

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

runtime/foundation/settings_service.gd

@@ -0,0 +1,43 @@
+class_name ABGSettingsService
+extends RefCounted
+
+const StoreScript = preload("res://entry/settings_store.gd")
+const SETTINGS_VERSION := StoreScript.SETTINGS_VERSION
+const TEXT_SCALES := StoreScript.TEXT_SCALES
+const SAFE_AREA_PRESETS := StoreScript.SAFE_AREA_PRESETS
+
+## Application-facing Settings boundary. The existing JSON schema, migration,
+## validation and atomic file protocol remain owned by the proven backend; new
+## pages depend on this boundary rather than opening a settings file directly.
+
+var backend
+
+var path: String:
+	get:
+		return String(backend.path)
+	set(value):
+		backend.path = value
+
+
+func _init(existing_backend = null) -> void:
+	backend = existing_backend if existing_backend != null else StoreScript.new()
+
+
+func defaults() -> Dictionary:
+	return backend.defaults()
+
+
+func load_settings() -> Dictionary:
+	return backend.load_settings()
+
+
+func save_settings(value: Dictionary) -> Dictionary:
+	return backend.save_settings(value)
+
+
+func validate(value: Dictionary) -> Dictionary:
+	return backend.validate(value)
+
+
+func backend_type_name() -> String:
+	return backend.get_script().resource_path.get_file()