Network disconnect: Show sidewalk no indicators

I noticed that, when reviewing the network disconnects, that I think it would be helpful to have an indicator that there is an explicit "no" mapped.

Example:

https://a-b-street.github.io/speedwalk/#16.69/52.768452/13.31836

All the roads that dont have any lines are in fact right, but I have to switch to iD to see this.

The issue is about adding a visual indicator for explicitly mapped 'no' sidewalk ways in the speedwalk map interface. Start by examining the frontend code in the repository, likely in Svelte components that render the map tiles and network disconnect overlays. Look for where road features are styled and how 'no' sidewalk data is currently handled. The goal is to modify the rendering logic to show a distinct indicator (like a line or symbol) for roads where sidewalks are explicitly tagged as absent in OSM.

Written by the indexing model from the issue text.