store_set_primary_mockup

Mark a mockup as the primary hero for its product.

Sets is_primary=true on the mockup row. Side effects: demotes sibling mockups for the same master_product_id, and pushes mockup_url into hero_image_url_override on every matching store_products listing — so the storefront immediately shows the new hero.

{
  "slug": "string",
  "mockup_id": "uuid"
}

{
  "ok": true,
  "mockup_id": "uuid",
  "affected_store_products": "number"
}

{
  "name": "store_set_primary_mockup",
  "arguments": { "slug": "bravo", "mockup_id": "4d5e6f70-…" }
}