/news: wear the shared HubBar (consistent chrome), keep BottomNav + global footer

Per the agreed direction (Codex calls): /news joins the new family without CD.
- NewsFeed gets an explicit chrome="legacy|hub" prop (never inferred from path):
  `/` passes legacy (its own Header, unchanged) and /news passes hub (the shared
  editorial HubBar). Exactly one bar renders — never HubBar + Header.
- HubBar gains a configurable `newsHref`; the /news instance links News → /news
  (active), not the live `/`. Other hub pages keep the default (News → /).
- BottomNav kept (Highlights/Latest/Play/You stay visible); no top-level Back on
  bare /news (HubBar Home returns to the hub); contextual Back on drill-in views
  is unchanged. No new footer — the global footer stays until the shared Footer step.

Known prominence shift (refinable later): Saved/Boundaries move off the top bar on
/news (reachable via account); Feedback stays via the global footer. /news still
noindex. 32 tests green; build clean.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

frontend/src/routes/+page.svelte

@@ -5,4 +5,4 @@
   import NewsFeed from '$lib/components/NewsFeed.svelte';
 </script>
 
-<NewsFeed />
+<NewsFeed chrome="legacy" />

frontend/src/routes/news/+page.svelte

@@ -9,4 +9,4 @@
   <meta name="robots" content="noindex, follow" />
 </svelte:head>
 
-<NewsFeed />
+<NewsFeed chrome="hub" />