- Created StageRuntimeConfig and StageConfig dataclasses - Implemented StageConfigFactory with builder pattern - Added _get_device_string() helper for device enumeration - Refactored _create_default_diffusion_stage_cfg() to use factory - Added comprehensive unit tests for new config builder - Delegated cache config methods to factory - Updated both Omni and AsyncOmni classes Co-authored-by: hsliuustc0106 <222337142+hsliuustc0106@users.noreply.github.com>