Give render and the draw fences one pin set

doc.go

@@ -28,7 +28,8 @@ package fejkdata
 //   - draw group — reference draws held apart inside one render:
 //     `template.drawGroup` as the data spells it, `template.drawGroupKey` as a
 //     render reads it, `holdSet`, `renderScope`.
-//   - pin — fixing which row of a table the render uses: `hold.pin`, `hold.rowOf`.
+//   - pin — fixing which row of a table the render uses, which the draw fences replay:
+//     `pinSet`, `pinSet.pin`, `pinSet.rowOf`.
 //   - family — a table and every table reaching it through a chain of
 //     `table.parentT`, named by the root that chain ends at: `table.family`.
 //   - whole — a read that lands on a `row`, so the row renders through its table's