fix(ui): E31 S2 — the tab names the object, the channel header wraps, the player fits a short window

- The browser tab names the place and the object: PageHeading reports the
  view's own title (lib/documentTitle), so a channel, playlist or any Plex
  view reads "<object> · <module> · Siftlode" however it was opened; the
  Feed is named too; a season adds its show (tabTitle).
- The channel page's tab + action row wraps and lets the tag lane fold into
  "+N": at 1024 it ran past the edge and the page scrolled sideways.
- The YouTube player card's width is capped from the window height less the
  chrome measured under the video: at 133% zoom (685px) it cut its channel row.
- Plex certificate words (Not Rated, Approved, Passed) are named through the
  vocabulary on the info badge, show page, collection, filter and chips.
- DESIGN.md: the zoom target is 125% and 133%, not 200% (decision log).

frontend/src/components/PlexCollectionView.tsx

@@ -1,5 +1,6 @@
 import { useState } from "react";
 import { useTranslation } from "react-i18next";
+import { vocab } from "../lib/vocab";
 import { useQuery, useQueryClient } from "@tanstack/react-query";
 import { Play, Shuffle, Pencil, Trash2, Plus, X, Lock, Check, Search } from "lucide-react";
 import { qk } from "../lib/queryKeys";
@@ -262,7 +263,7 @@ export default function PlexCollectionView({
   const meta = [
     d?.year_min != null &&
       (d.year_max && d.year_max !== d.year_min ? `${d.year_min} — ${d.year_max}` : `${d.year_min}`),
-    d?.content_rating,
+    d?.content_rating && vocab(t, "certificate", d.content_rating),
     d && t("plex.browse.items", { count: d.child_count ?? items.length }),
     formatRuntime(d?.total_runtime_s, lang),
   ].filter(Boolean) as string[];