v0.19.0

Released 2026-09-26. Every package in the workspace moves to 0.19.0 together, and so do
dirigent-dhis2 and dirigent-integration.

• The playground: an instance answers its own test requests. Five paths under
  /api/v1/playground/, unauthenticated and off by one setting, that reflect what they were
  called with and answer the way a document needs them to: a request echoed back whole, a
  chosen status, a redirect that stays on this instance, an endpoint that fails a set number
  of attempts before succeeding, and one that sets the response headers you name. Every
  answer carries the request that produced it under one key, and the resolved knobs beside
  it, so what was sent and what was used are both on screen.
• A node that makes data, anywhere in a flow. playground.generate takes a field map
  naming the Faker provider that fills each field, so every provider the installed Faker
  offers is reachable in every locale, reproducible under a seed the answer always reports.
  It also fails on demand, delays, drifts its own shape, pages, and pads its payload, so a
  retry example really retries, a gate is really seen catching drift, and an outputs-to-
  storage example really crosses the threshold. It works with no input as a document's first
  step, with an input from upstream in the middle, and as the last step.
• A shelf of five documents that teach exactly those cases, runnable with no network.