Submit an asynchronous Storyboard image generation task. Returns a taskId for polling results via the Query Task API.The system converts the user's story text (and optional reference images) into a storyboard grid preview image (Stage 1; does not include subsequent video generation). Models: Supports GPT Image 2, Nano Banana 2, and Nano Banana Pro (pass displayName or model code; case-insensitive). Parameter rules: - story is required, max 5000 characters- aspectRatio on the public API only supports 16:9, 9:16, 1:1; default 16:9 - resolution is required; allowed values vary by model: GPT Image 2 / Nano Banana Pro → 1K/2K/4K; Nano Banana 2 → 512p/1K/2K/4K- gridMode supports auto / preset / custom; default preset - When gridMode=preset, gridSize must be 4 / 9 / 25; default 9 - When gridMode=custom, gridSize supports 2~25- targetDurationSeconds defaults to 15; must be ≥ 1 - referenceFileIds is an optional list of image fileIds; GPT Image 2 max 16, Nano Banana 2 max 14, Nano Banana Pro max 6 Credits: Charged after task completion. Use costCredit in the query response to check consumption. Common error codes: - 4000: Invalid parameters (empty story, unsupported aspectRatio/resolution, invalid gridSize, etc.) - 4100: Insufficient credits - 5000: Internal server error