Use tall destination preview volume

docs/PORTING.md

@@ -127,6 +127,10 @@ Version 0.1.16 makes destination previews sample a centered 17-by-7-by-17
 volume. The Ponder scene uses a scale that keeps its full horizontal diagonal
 inside the panel, so the complete snapshot remains available during its orbit.
 
+Version 0.1.17 changes destination previews to a 9-by-128-by-9 volume: a
+square horizontal footprint with a vertical slice spanning 64 blocks below and
+63 blocks above the recorded linking location.
+
 The preview code is separated behind a renderer interface and uses an isolated
 Ponder level populated from server-authoritative destination snapshots.