Turns a raw, half-formed task description into a high-quality Fable 5 prompt by first hunting the user's blind spots. Use when the user invokes /prompt-prep, asks to 'prepare/improve/refine a prompt', or hands over a task that is underspecified in ways they probably haven't noticed. Based on Thariq Shihipar's (Anthropic) Fable 5 prompting method: quality is limited by unfound unknowns, not by the model.
