v0.2.0

Changed

• The error for "the gate left nothing registered" now names the switch as well
  as its wording — it ends … suppresses, but THING_READ_ONLY is set … where it
  previously stopped at the wording.

  Found while migrating the first server off its own copy, whose message had
  always named the variable. It is the more severe of the two gate errors — the
  server does not start at all — and it was the less actionable one, while the
  milder "you named a suppressed tool" already said which variable to unset.

  Minor rather than patch because the text is what callers assert on.