- a kind no plugin registered always inserts through the insert-only River
client, so Dispatch and Enqueue no longer fail River's unknown-kind check
while the in-process worker runs
- while a worker runs, such a kind must name a queue no worker serves;
an empty queue, default, scheduled, a configured queue or a registered
job's queue is ErrUnregisteredKindQueue and nothing is written
- README and docs/services/jobs.md describe jobs whose worker ships later
- docs/services/jobs.md: declaring, registering and dispatching jobs, the
summer_jobs record, progress, cancellation and workers
- conga ExampleJob plus dispatch and status regions run by TestDocsDispatch
on the package's Postgres harness (DocsApp in export_docs_test.go)
- concept map links the queued jobs row; services/jobs is a required page
