Thumbnail Generation Skill Generate song cover/thumbnail images using Google Gemini's image generation API. Output images can be used directly as MV backgrounds with the acestep-simplemv skill. API Key Setup Guide Before generating, you MUST check whether the user's API key is configured. Run the following command to check: This command only reports whether the API key is set or empty — it does NOT print the actual key value. NEVER read or display the user's API key content. Do not use on key fields or read directly. The command is safe — it automatically masks API keys as in output. If the c…