feat(admin): open controller-link settings entries from the settings index

A settings entry with a controller opens that controller's route from
its card (settingsPath); singleton cards still open /settings/<code>.
On a linked controller with no navigation entry of its own the rail
marks Settings current, the breadcrumbs read Settings > entry label
(plus the record title on record and create routes) and the page title
uses the entry label. The settings docs describe the admin behaviour;
the embedded admin shell is rebuilt.

admin/tests/shell/Breadcrumbs.test.ts

@@ -72,6 +72,37 @@ describe('breadcrumbs', () => {
     expect((await crumbsAt('/settings/unknown')).labels).toEqual(['Ustawienia'])
   })
 
+  it('reads Ustawienia and the entry label on a settings-linked controller', async () => {
+    const locales = { ...settingsFixture.list.data[0]!, code: 'locales', label: 'Locales', model: '', controller: 'acme.lang.locales' }
+    const crumbsWithLink = async (path: string) => {
+      await signIn()
+      setNavigation(navigationFixture.data)
+      setSettings([...settingsFixture.list.data, locales])
+      const router = await routerAt(path)
+      const wrapper = mount(Breadcrumbs, { global: { plugins: [router] } })
+      await flushPromises()
+      const items = wrapper.findAll('[data-crumb]')
+      return {
+        labels: items.map((item) => item.text()),
+        links: items.map((item) => (item.find('a').exists() ? item.find('a').attributes('href') : null)),
+        current: items.map((item) => item.find('[aria-current="page"]').exists()),
+      }
+    }
+    let crumbs = await crumbsWithLink('/acme/lang/locales')
+    expect(crumbs.labels).toEqual(['Ustawienia', 'Locales'])
+    expect(crumbs.links).toEqual(['/settings', null])
+    expect(crumbs.current).toEqual([false, true])
+
+    setRecordCrumb('Polish')
+    crumbs = await crumbsWithLink('/acme/lang/locales/3')
+    expect(crumbs.labels).toEqual(['Ustawienia', 'Locales', 'Polish'])
+    expect(crumbs.links).toEqual(['/settings', '/acme/lang/locales', null])
+
+    setRecordCrumb('')
+    crumbs = await crumbsWithLink('/acme/lang/locales/create')
+    expect(crumbs.labels).toEqual(['Ustawienia', 'Locales'])
+  })
+
   it('is empty outside any permitted plugin', async () => {
     expect((await crumbsAt('/acme/secret/things')).labels).toEqual([])
     expect((await crumbsAt('/acme/demo/unlisted')).labels).toEqual(['Demo'])