v0.21.0

Released 2026-09-27. Every package in the workspace moves to 0.21.0 together, and so do
dirigent-dhis2 and dirigent-integration.

• A watch keeps a sensor waiting. A third trigger beside schedules and webhooks, declared
  under triggers: watches: in a pipeline document or a kind: triggers document. A watch
  keeps exactly one run of its pipeline waiting on one root sensor step; when that step
  succeeds, the same transaction arms the next run, and the run that succeeded carries on
  downstream. Runs overlap by design: one batch is being transformed while the next is being
  waited for. A run that ends without its sensor succeeding re-arms from the last good point
  after a backoff that doubles from watch_backoff to watch_backoff_max. Apply refuses a
  watch on a step that is unknown, not a root, fans out, is not a sensor, or sits in a
  replace pipeline, and a later version that would break one.
• The cursor belongs to the watch. A sensor's success can say where it left off:
  Sensor.resume_cursor(output), with a default of none, so every existing sensor starts each
  run fresh as before. The watch stores what it returns and seeds the next run with it, which
  the block reads through ctx.cursor. kafka.consume continues its offsets across runs with
  no consumer group, and playground.arrive numbers each batch on from the last. Pausing
  keeps the cursor, and resuming arms a run from it. dirigent-testing gains carry_cursor,
  which hands a sensor's next poke what the engine would.
• dg watch lists, shows, pauses and resumes watches, writing watch, watch.paused and
  watch.resumed records; the API has the same four routes under
  /pipelines/{code}/triggers/watches. dg dev --seed, dg apply --paused and
  dg run --local create watches paused, so a demo or a single local run is never competing
  with one.
• The Triggers screen lists watches beside schedules and webhooks, with their state,
  cursor, failures and last error, and so do the pipelines listing and the pipeline tab.
• Two documents teach it: triggers/watch-a-sensor.yaml over playground.arrive, runnable
  with no network, and queues/kafka-watch-then-transform.yaml over a real topic.
• The New connection form suggests the playground as its example code, not a service the
  corpus has left.