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/plexViews.tsx

@@ -583,7 +583,7 @@ export function PlexShowView({
                       : undefined
                   }
                 >
-                  {show.content_rating}
+                  {vocab(t, "certificate", show.content_rating)}
                 </Filterable>
               )}
               {show.season_count != null && (
@@ -838,7 +838,10 @@ export function PlexSeasonView({
             <Button variant="link-muted" selectable onClick={onBack} className="text-sm">
               {d.show.title}
             </Button>
-            <PageHeading className="text-2xl font-semibold leading-tight">
+            <PageHeading
+              className="text-2xl font-semibold leading-tight"
+              tabTitle={`${d.show.title} · ${seasonTitle(se, t)}`}
+            >
               {seasonTitle(se, t)}
             </PageHeading>
             <p className="text-sm text-muted mt-1">