Add direction arrow on generic link

When generic links are created, there is an implicit direction, which is important when performing matching and action code. However, this is not shown visually.

Proposal: Add an arrow to the generic link concrete syntax to show the direction of connection.

Start by locating the generic link concrete syntax and the part of the project that renders it visually. Check how the link direction is currently represented for matching and action code, then verify that the rendered generic link visibly includes an arrow without changing its direction behavior.

Written by the indexing model from the issue text.