feat(shell): draw only the destinations the user kept

The navigation reads the resolved map from the backend rather than
holding a copy of the defaults, which would be the copy that shipped in
the binary rather than the one being edited.

Hiding takes away the nav item and nothing else: `navigate` still
resolves a hidden view, which detail views and the launch page depend
on. No special case was needed for the highlight, because #72 moved
that onto `active-view-store` -- the sidebar asks `isActive(id)` per
*rendered* item, so a hidden view lights nothing exactly as a detail
view does.

Downloads is gated at the nav on `downloadStore.available` rather than
in the config, so switching it on in Settings still means what it says
once a client exists, and the tab appears without a restart. `available`
is false until the providers have loaded, which makes the item appear on
a fresh launch rather than appearing and then vanishing.

The tab bar honours the toggles too, and the reason is local rather than
a general rule about phones: "More" opens the *same* `<app-sidebar>`,
which filters, so an unfiltered bar would contradict its own drawer one
tap away. Which four tabs is still plan 016's subset; this only removes
from it, and "More" is never filtered.

`services/view-meta.ts` is the destination list, on `shortcut-meta.ts`'s
pattern, because Settings is now a second reader of the same labels in
the same order.

Two existing sidebar tests had to say which world they describe: eleven
destinations now assumes a configured download client.

frontend/test/components/keyboard-reach.test.ts

@@ -11,7 +11,8 @@ import { describe, expect, it, beforeEach } from 'vitest';
 import '@components/sidebar/app-sidebar';
 import '@components/queue-panel/queue-panel';
 import '@components/track-list/track-list';
-import { stub } from '@test/support/harness';
+import { stub, emit, flush } from '@test/support/harness';
+import { Events } from '../../src/events';
 import { fixture, shadow, shadowAll, update } from '@test/support/render';
 
 /** Two fixture tracks, enough to move a focus ring between. */
@@ -33,6 +34,16 @@ const TRACKS = [
 ] as never[];
 
 describe('<app-sidebar> is reachable', () => {
+  // Eleven destinations assumes a configured download client, since
+  // Downloads is not offered without one (#25).
+  beforeEach(async () => {
+    stub('download.Service.ListProviders', [
+      { id: 1, kind: 'slskd', name: 'Sound', enabled: true, priority: 50 },
+    ]);
+    emit(Events.DownloadProvidersChanged);
+    await flush();
+  });
+
   it('renders every destination as a button, not a bare list item', async () => {
     const el = await fixture('app-sidebar');