feat(plex): move Watch-state out of the rail into a toolbar pill

The "Show" (watch-state) filter leaves the left rail and becomes a FilterSelect
pill next to the item count, mirroring the feed's Watch-state control — a
top-level "what am I looking at" choice, always in reach, not buried in the rail.
It still emits a removable chip when non-default (same as the feed).

frontend/src/components/PlexSidebar.tsx

@@ -27,7 +27,6 @@ type Props = {
   onToggleCollapse: () => void;
 };
 
-const SHOW_OPTS = ["all", "unwatched", "in_progress", "watched"] as const;
 const RATING_STEPS = [5, 6, 7, 8, 9];
 const ADDED_OPTS = ["24h", "1w", "1m", "6m", "1y"] as const;
 const DURATION_BUCKETS: { key: string; min: number | null; max: number | null }[] = [
@@ -66,7 +65,7 @@ export default function PlexSidebar({ layout, setLayout, collapsed, onToggleColl
   // the header search box); this rail is the primary editor of them. Opening a playlist is a
   // hand-off to PlexBrowse via the shared `playlistOpen` slot.
   const { scope, show, filters } = usePlex();
-  const { setShow, setFilters, setPlaylistOpen: onOpenPlaylist } = usePlexActions();
+  const { setFilters, setPlaylistOpen: onOpenPlaylist } = usePlexActions();
   const playlistsQ = useQuery({ queryKey: qk.plexPlaylists(), queryFn: () => api.plexPlaylists() });
   const [newPlaylist, setNewPlaylist] = useState("");
   // This rail's media source (the Plex library) — names the abstraction the feed and Plex rails
@@ -151,18 +150,6 @@ export default function PlexSidebar({ layout, setLayout, collapsed, onToggleColl
         </>
       ),
     },
-    {
-      id: "watch",
-      title: t("plex.filter.show"),
-      body: (
-        <FilterChipGroup
-          ariaLabel={t("plex.filter.show")}
-          options={SHOW_OPTS.map((s) => ({ value: s, label: t(`plex.filter.showOpt.${s}`) }))}
-          value={show}
-          onChange={setShow}
-        />
-      ),
-    },
     ...(peopleActive
       ? [
           {