make failure messages useful
RenderTree.diff()
use String instead of Cord in RenderedTree (because it implements equal(), and these labels should never be large anyway)
RenderTree instance for Term
update tests
use MakeArrayN consistently
update sort/filter expectations
remove unused OrderBy cases; clean up use of NonEmptyList
update test to accept result with temp field left over; tests on hand-written logical plans
propagate pipelines from sort keys
reinstate simpler handling of sorting on simple derefs

Restores simpler plan for simple cases, preserving source collection's shape.

A specific error, with an explanation of the cause