feat(11.1-04): add the Services section with a verified Queued jobs page

- 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

cmd/summer/docs_test.go

@@ -93,6 +93,7 @@ var requiredPages = []string{
 	"console/scaffolding",
 	"console/writing-commands",
 	"console/utilities",
+	"services/jobs",
 }
 
 // TestDocsRequiredPages asserts that every required page is in the loaded