shorts-reels: several cheap vertical drafts, then promote the winner

Short-form social wants options, not one perfect clip. This skill turns "give me five vertical clips" into a priced batch on the catalog's cheap tier, a contact sheet to pick from, and a single re-render of whichever one earned it.

This skill is a thin, scenario-specific layer over ofox-video-core. It owns the vertical format, the draft-then-promote ladder and the batch economics; ofox-video-core owns talking to the Ofox API correctly and safely (the OFOX_API_KEY handling, the no-resubmit rule, error-code mapping, download/verification, the contact sheet, and reporting absolute paths). Read that skill's safety contract before using this one — it is not restated here.