Function sheet_rung 

fn sheet_rung(
    recipe: &CurveRecipe,
    entry: &SheetEntry,
    template: &AnyTemplate,
    code: &str,
    market: &MarketContext,
    notional: f64,
) -> Result<Rung, RecipeQuoteError>

One sheet entry’s rung, dispatched on the template’s family and the locator’s shape.