v0.20.0

Released 2026-09-26. Every package in the workspace moves to 0.20.0 together, and so do
dirigent-dhis2 and dirigent-integration.

• The corpus runs on its own instance. Every example and every page of the documentation
  is off postman-echo.com. A document that needed something to happen -- a list to fan out
  over, a step that fails twice, a delay against a timeout, a payload over the storage
  threshold -- now says so with the playground.generate node, so it runs offline and under
  dg run --local with no connection and no URL. A document that is teaching http.request
  itself still makes a real call, to this instance's own playground. The basics tutorial is
  rewritten and re-shot on it.
• A step that waits, with nothing to wait for. playground.arrive parks for a number of
  pokes or a length of time and then yields a batch, so a readiness wait can be taught and
  verified with no service to poll. Its output is the shape a queue consumer answers with,
  so a document that later reads a real topic changes very little.
• A stream to test a consumer against. /api/v1/playground/stream writes newline-delimited
  JSON: an envelope, then a message every interval, then a closing line, so a reader can tell
  an ending from a dropped connection.
• A failure can say what kind it is. fail_as beside fail_until names the class the
  induced failure carries, so the difference between a transient failure that spends the
  retry budget and a rejected one that spends none can be taught offline, on three steps
  under one policy. Before this, a document could only get a rejected failure from a live
  HTTP call or by naming a Faker provider that does not exist.
• An unknown provider names a command that exists. The refusal for a Faker provider the
  installed library does not have pointed at a route that was never served.