cli: change link direction symbols — heartwood

The symbols used for inbound and outbound are part of the Supplementary Multilingual Plane (or Plane 1). This set of symbols are not as well supported by font sets, as discovered by many reports of the characters missing.

There are two other arrow characters: south east and north east that serve the same style and are part of the Basic Multilingual Plane (or Plane 0). This set of characters is more widely supported.

 }
 fn link_direction_inbound() -> term::Paint<String> {
     term::format::yellow("🡦".to_string())
     term::format::yellow("↘".to_string())
 }
 fn link_direction_outbound() -> term::Paint<String> {
     term::format::dim("🡥".to_string())
     term::format::dim("↗".to_string())
 }