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

e2e/specs/page-header.spec.ts

@@ -21,7 +21,6 @@ const VIEWS: [string, string, boolean][] = [
   ['tracks', 'Tracks', true],
   ['explore', 'Explore', false],
   ['downloads', 'Downloads', false],
-  ['jobs', 'Background jobs', false],
 ];
 
 /** The header lives in the view's shadow root, inside its own. */
@@ -53,7 +52,6 @@ const TAGS: Record<string, string> = {
   tracks: 'track-list',
   explore: 'explore-view',
   downloads: 'downloads-view',
-  jobs: 'jobs-view',
 };
 
 test.describe('every primary view says what it is', () => {