test: cover jobs in Settings, and unpick two shared selectors

The spec worth having is not that the tab is gone -- that is one line
of a table -- but that nothing became unreachable when it went. #24
promises that no action is ever unreachable at any supported size, and
deleting a destination is exactly the change that quietly breaks it.

Two existing selectors had to give. `config-section .header` is
ambiguous the moment a section holds a job, because `job-details-drawer`
carries that class too -- so `settings-reach.spec.ts` locates a
disclosure by role and name instead. And `page-header`'s and
`offline-icons`'s view lists lose an entry each.

Closes #27

frontend/test/components/view-lifecycle.test.ts

@@ -27,7 +27,6 @@ import '@components/explore-view/explore-view';
 import '@components/home-view/home-view';
 import '@components/downloads-view/downloads-view';
 
-import '@components/jobs/jobs-view';
 import '@components/playlist-view/playlist-view';
 import { fixture } from '@test/support/render';
 import { stub, flush } from '@test/support/harness';
@@ -223,7 +222,6 @@ const CACHED_VIEWS = [
   'artists-view',
   'genres-view',
   'downloads-view',
-  'jobs-view',
   'playlist-view',
   'explore-view',
   'home-view',