Consider using geom_lineribbon and step="mid" for quantile-based figures

[damonbayer]

I think using geom_lineribbon could save you complexity in the plot code.

I also think using a "mid" step might make the forecasts more readable at smaller sizes. It has the effect of making the forecasts seem "wider" in the x axis, so you can more easily tell if a particular data point is captured by the relevant credible interval. This may still be lost at the daily resolution, though.

Example from previous work that used a weekly resolution: