Refine a YouTube video idea into a structured production brief with angle, key points, value proposition, CTA asset, and audience segment. Use this skill whenever the user says "create a brief", "brief this idea", "develop this idea", "write a video brief", "production brief", or has selected a video idea from ideation and wants to define the angle and structure before packaging and outlining. Use when working with yt brief. Trigger with 'yt', 'brief'.