polygon mesh

We already have --detect-shared-borders:

> -ab or --detect-shared-borders: In the manner of TopoJSON, detect borders that are shared between multiple polygons and simplify them identically in each polygon. This takes more time and memory than considering each polygon individually.

How about a mesh option like https://github.com/topojson/topojson-client#mesh which extracts shared borders from polygons and creates a single line?

This is useful when creating a map of parcel boundaries as lines only, where you don't need the original polygon as it avoids overlapping lines which can improve how it renders visual. Not sure if it would decrease or increase the file size.

Start by reading the existing --detect-shared-borders option and the linked TopoJSON mesh reference. Define how a new mesh option should extract shared polygon borders into a single line, then verify its behavior on parcel-boundary data and confirm whether the resulting output changes file size.

Written by the indexing model from the issue text.