Name a read's context its group, route and branches, deleting surveyAt

doc.go

@@ -37,7 +37,7 @@ package fejkdata
 //   - family — a table and every table reaching it through a chain of
 //     `table.parentT`, named by the root that chain ends at: `table.familyRoot`.
 //   - whole — a read of a table with no selector and no descent, {/city}, landing on
-//     the `table` itself, so it draws a row apart from every pin: `surveyAt.wholePins`.
+//     the `table` itself, so it draws a row apart from every pin: `branches.wholePins`.
 //   - fence — a load-time check, so rendering a compiled tree cannot fail: `New`
 //     runs them over the data set, `NewTemplate` and `FakeStruct` over what those
 //     compile. The draw fences are `heldCheck`, `drawFence` and `checkFamilies`.